A08-ExponentProblems.mws

High School Modules > Algebra by Gregory A. Moore

     Exponent Problems


The rules of exponents, and solving problems with exponents.

[Directions : Execute the Code Resource section first. Although there will be no output immediately, these definitions are used later in this worksheet.]

0. Code

>    restart;

>    txln := `\n____________________________________________________________________________`:

1. Rules of Exponents


Here are some of the main rules of exponents, and their application in Maple.

>    print(cat(txln,`\n1. Product Rule`));
a^n * a^m: %= simplify(%);print(txln);

`\n____________________________________________________________________________\n1. Product Rule`
`\n____________________________________________________________________________\n1. Product Rule`
`\n____________________________________________________________________________\n1. Product Rule`

a^n*a^m = a^(n+m)

`\n____________________________________________________________________________`
`\n____________________________________________________________________________`

>    10^5 * 10^2;

10000000

>    x^5 * x^4;

x^9

>    y^8 * y^5;

y^13

>    (x+4)^10 * (x+4)^8;

(x+4)^18

>    x^4 * y^3; `Note that the bases must be the same to use this rule`;

x^4*y^3

`Note that the bases must be the same to use this rule`

>    distance^2 * distance^3;

distance^5

>    print(cat(txln,`\n2. Quotient Rule`));a^n / a^m: %= simplify(%); print(txln);

`\n____________________________________________________________________________\n2. Quotient Rule`
`\n____________________________________________________________________________\n2. Quotient Rule`
`\n____________________________________________________________________________\n2. Quotient Rule`

a^n/(a^m) = a^(n-m)

`\n____________________________________________________________________________`
`\n____________________________________________________________________________`

>    10^9 / 10^6;

1000

>    x^14/x^13;

x

>    x^20 / x^23;

1/(x^3)

>    q^100 / q^10;

q^90

>    (y + 7)^3 / (y+7)^5;

1/((y+7)^2)

>    print(cat(txln,`\n3. Zero Power is One`)); `a^0` = expand(a^0);print(txln);

`\n____________________________________________________________________________\n3. Zero Power is One`
`\n____________________________________________________________________________\n3. Zero Power is One`
`\n____________________________________________________________________________\n3. Zero Power is One`

`a^0` = 1

`\n____________________________________________________________________________`
`\n____________________________________________________________________________`

>    13^0;    813^0;      (-29)^0;       (3/19)^0;     (41239)^0;    (3.14159)^0;

1

1

1

1

1

1.

>    print(cat(txln,`\n4. Power of One is Identity`));`a^1` =simplify(a^1); print(txln);

`\n____________________________________________________________________________\n4. Power of One is Identity`
`\n____________________________________________________________________________\n4. Power of One is Identity`
`\n____________________________________________________________________________\n4. Power of One is Identity`

`a^1` = a

`\n____________________________________________________________________________`
`\n____________________________________________________________________________`

>    13^1;    813^1;      (-29)^1;       (3/19)^1;     (41239)^1;    (3.14159)^1;

13

813

-29

3/19

41239

3.14159

>    print(cat(txln,`\n5. Power of a Power`));  (a^n)^m = a^(n*m) ;     print(txln);

`\n____________________________________________________________________________\n5. Power of a Power`
`\n____________________________________________________________________________\n5. Power of a Power`
`\n____________________________________________________________________________\n5. Power of a Power`

(a^n)^m = a^(n*m)

`\n____________________________________________________________________________`
`\n____________________________________________________________________________`

>    (x^2)^3;

x^6

>    (y^10)^5;  `Compare with ...`, (y^10)*(y^5),` power of a power ­ product of powers`;

y^50

`Compare with ...`, y^15, ` power of a power ­ product of powers`

>    ((t - 7)^8 )^3 ;

(t-7)^24

>    print(cat(txln,`\n6. Power of Product`));  (a*b)^m = (a^n)*(b^m);  print(txln);

`\n____________________________________________________________________________\n6. Power of Product`
`\n____________________________________________________________________________\n6. Power of Product`
`\n____________________________________________________________________________\n6. Power of Product`

(a*b)^m = a^n*b^m

`\n____________________________________________________________________________`
`\n____________________________________________________________________________`

>    (3*x)^4;

81*x^4

>    (8*y)^10;

1073741824*y^10

>    print(cat(txln,`\n7. Power of a Product of Powers`));  
          (a^n*b^m)^m = (a^(n*p))*(b^(m*p));  
          `(This is a combination of rules 1 and 6.)`; print(txln);

`\n____________________________________________________________________________\n7. Power of a Product of Powers`
`\n____________________________________________________________________________\n7. Power of a Product of Powers`
`\n____________________________________________________________________________\n7. Power of a Product of Powers`

(a^n*b^m)^m = a^(n*p)*b^(m*p)

`(This is a combination of rules 1 and 6.)`

`\n____________________________________________________________________________`
`\n____________________________________________________________________________`

>    (x^3 * y^5) ^ 2;

x^6*y^10

>    (x^10 * y^20) ^ 5;

x^50*y^100

>    (17 * M^7) ^ 2;

289*M^14

>    (3 * x^10 * y^7) ^ 4;

81*x^40*y^28

>    (a^2 * b^3 * c^4 * d^5 ) ^ 10;

a^20*b^30*c^40*d^50

>    print(cat(txln,`\n8. Power of a Quotient`)); (a/b)^n =(a^n)/(b^n); print(txln);

`\n____________________________________________________________________________\n8. Power of a Quotient`
`\n____________________________________________________________________________\n8. Power of a Quotient`
`\n____________________________________________________________________________\n8. Power of a Quotient`

(a/b)^n = a^n/(b^n)

`\n____________________________________________________________________________`
`\n____________________________________________________________________________`

>    (3/4)^3;

27/64

>    (x/2)^5;

1/32*x^5

>    (a/b)^4;

a^4/b^4

>    (3/(x+5))^9;

19683/(x+5)^9

>    print(cat(txln,`\n9. Power of a Quotient of Powers`));
                 (a^n * b^m)^p =  a^(n*p)*b^(m*p);
               `(This is a combination of rules 2 and 8.)`; print(txln);

`\n____________________________________________________________________________\n9. Power of a Quotient of Powers`
`\n____________________________________________________________________________\n9. Power of a Quotient of Powers`
`\n____________________________________________________________________________\n9. Power of a Quotient of Powers`

(a^n*b^m)^p = a^(n*p)*b^(m*p)

`(This is a combination of rules 2 and 8.)`

`\n____________________________________________________________________________`
`\n____________________________________________________________________________`

>    ( x^3 / y^ 5)^2;

x^6/y^10

>    ( 1 / pressure^2) ^ 3;

1/(pressure^6)

>    (x^10 / 3) ^ 5;

1/243*x^50

2. Negative Exponents


There are a few more rules which involve negative exponents.

>    print(cat(txln,`\n10.  Negative Exponent is Reciprocal`));
                      a^(-n) =  1/a^n;        print(txln);

`\n____________________________________________________________________________\n10.  Negative Exponent is Reciprocal`
`\n____________________________________________________________________________\n10.  Negative Exponent is Reciprocal`
`\n____________________________________________________________________________\n10.  Negative Exponent is Reciprocal`

a^(-n) = 1/(a^n)

`\n____________________________________________________________________________`
`\n____________________________________________________________________________`

>    3^(-2);

1/9

>    `Note :`, 9*3^(-2), 9*(1/9);

`Note :`, 1, 1

>    x^(-13);

1/(x^13)

>    (-2)^(-3);

-1/8

>    (-2)^(-4);

1/16

>    (1/7)^(-2);

49

>    print(cat(txln,`\n11. Reciprocal of a Reciprocal is Original`));
                      1/a^(-n) =  a^n;        print(txln);

`\n____________________________________________________________________________\n11. Reciprocal of a Reciprocal is Original`
`\n____________________________________________________________________________\n11. Reciprocal of a Reciprocal is Original`
`\n____________________________________________________________________________\n11. Reciprocal of a Reciprocal is Original`

1/(a^(-n)) = a^n

`\n____________________________________________________________________________`
`\n____________________________________________________________________________`

>    1/(4^(-3));

64

>    1/y^(-12);

y^12

>    1/(3*x + 2)^(-5);

(3*x+2)^5

>    `Note : Rules 10 and 11 can both be used on the same problem :`;x^(-4) / y^(-9);

`Note : Rules 10 and 11 can both be used on the same problem :`

1/x^4*y^9

>    print(cat(txln,`\n12. Reciprocal of a Fraction is Flipped`)); (a/b)^(-n) =  (b/a)^n;  print(txln);

`\n____________________________________________________________________________\n12. Reciprocal of a Fraction is Flipped`
`\n____________________________________________________________________________\n12. Reciprocal of a Fraction is Flipped`
`\n____________________________________________________________________________\n12. Reciprocal of a Fraction is Flipped`

(a/b)^(-n) = (b/a)^n

`\n____________________________________________________________________________`
`\n____________________________________________________________________________`

>    (2/131)^(-1);

131/2

>    (x/y)^(-1);

1/x*y

>    (1000/A)^(-1);

1/1000*A

>    ( (x+1) / (x+2) )^(-1);

1/(x+1)*(x+2)

>    ( (x^2 + 3*x + 1) / (x^2 + 5*x + 2) )^(-1);

1/(x^2+3*x+1)*(x^2+5*x+2)

>    (( A/B )^(-1))^(-1);

A/B

3. Exponent Problems - Products (Monomials)


When multiplying two monomial expressions, numbers can be multiplied, and the same variables can be multiplied - remember that we learned in Rule #1 that we can only multiply variables with the same base. For example, with two expressions with numbers, x, and y's - you multiply :
         - number by number
         - x term by x term
         - y term by y term

>    (3 * x^7* y^2) * (4 * x^4 * y^9);

12*x^11*y^11

>    (5 * x^5 * y^2) * (11 * x^11 * y^(-3));

55*x^16/y

>    (13 * x^(-3)* y^(-8)) * (4 * x^(-2) * y^(-7));

52/x^5/y^15

>    (1440 * x^100* y^100) * (1200 * x^100 * y^(-100));

1728000*x^200

>    (33 * x^33* y^22) * (4 * x^44 * y^55);

132*x^77*y^77

4. Exponent Problems - Products (Using Distributive Property)


When we multiply a term by a sum or difference we need to use the Distributive Property.

>    `Distributive Property`; a*(b+c): % = expand(%);

`Distributive Property`

a*(b+c) = a*b+a*c


We distribute the term being multiplied to each of the terms inside the parentheses. Then each of those multiplications is a product of monomials.

>    (12*x^10)*(14*x^3 - 1): % = expand(%);

12*x^10*(14*x^3-1) = 168*x^13-12*x^10

>    (3*x^2)*(14*x + 21): % = expand(%);

3*x^2*(14*x+21) = 42*x^3+63*x^2

>    (2*x^5)*(4*x^5 - x^2): % = expand(%);

2*x^5*(4*x^5-x^2) = 8*x^10-2*x^7

>    (a^5*b^10)*(10*a^10*b^9 - a^8*b^7): % = expand(%);

a^5*b^10*(10*a^10*b^9-a^8*b^7) = 10*a^15*b^19-a^13*b^17

>    (20*a^5*b)*(13*a^4*b^9 - b^2): % = expand(%);

20*a^5*b*(13*a^4*b^9-b^2) = 260*a^9*b^10-20*a^5*b^3

5. Exponent Problems - Quotients - The Idea

 

6. Exponent Problems - Quotients - Using Maple


We can do these problems in Maple too - quite quickly. Try these by hand, and then check to see if your answer agrees with Maple's answer, or is mathematically equivalent.

>    (36 * x^4 * y^6 ) / (24 * x^5 * y^5);

3/2/x*y

>    (75 * x^10 * y^3 ) / (24 * x * y^5);

25/8*x^9/y^2

>    (100 * x * y ) / (45 * x^11 * y^9);

20/9/x^10/y^8

>    (32 * x^14 * y^6 ) / (40 * x^5 * y^5);

4/5*x^9*y

>    (10 * x^(-4) * y^(-6) ) / (12 * x^5 * y^5);

5/6/x^9/y^11

>    (33 * x^(-5) * y^6 ) / (22 * x^(-5) * y^(-5));

3/2*y^11

>    (15 * x^4 * y^(-6) ) / (18 * x^(-4) * y^5);

5/6*x^8/y^11

>    ((6 * x^2 * y^3) / (30 * x^4 * y^5 ) ) ^(-1) ;

5*x^2*y^2

>    ((40*x^2*y^9) / (30*x^(-6)*y^8) )^(-2) ;

9/16/x^16/y^2

>    ((27 * x^(-32) * y^19) / (24 * x^(-46) * y^8) )^(-4) ;

4096/6561/x^56/y^44


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