Big Ideas Math Algebra 2, 2014
BI
Big Ideas Math Algebra 2, 2014 View details
1. nth Roots and Rational Exponents
Continue to next subchapter

Exercise 5 Page 237

Practice makes perfect
a To evaluate the expression without a calculator, we should first rewrite it as a power involving a radical.

4^(3/2)
4^(1/2 * 3)
(4^(1/2))^3

a^(1/2)=sqrt(a)

(sqrt(4))^3
Having rewritten the expression as a power involving a radical, it is now easier to calculate. The square root of 4 is the number you have to multiply by itself to obtain 4, which is 2.

(sqrt(4))^3
(sqrt(2^2))^3
2^3

Next, we want to calculate 2^3, which is 2 multiplied by itself 3 times.

2^3

a^3=a* a* a

2* 2* 2
(2* 2)* 2
4* 2
8

b To evaluate the expression without a calculator, we should first rewrite it as a power involving a radical.

32^(4/5)
32^(1/5 * 4)
(32^(1/5))^4
(sqrt(32))^4
Having rewritten the expression as a power involving a radical, it is now easier to calculate. The fifth root of 32 is the number you have to multiply by itself five times to obtain 32, which is 2.

(sqrt(32))^4
(sqrt(2^5))^4
2^4

Next we want to calculate 2^4, which is 2 multiplied by itself 4 times.

2^4
2* 2* 2* 2
(2* 2)* (2* 2)
4* 4
16

c Like in Parts A and B, we should first rewrite the expression as a power involving a radical.

625^(3/4)
625^(1/4 * 3)
(625^(1/4))^3
(sqrt(625))^3
Having rewritten the expression as a power involving a radical, it is now easier to calculate. The fourth root of 625 is the number you have to multiply by itself four times to obtain 625, which is 5.

(sqrt(625))^3
(sqrt(5^4))^3
5^3

Next we want to calculate 5^3, which is 5 multiplied by itself 3 times.

5^3

a^3=a* a* a

5* 5* 5
(5* 5)* 5
25* 5
125

d Like in Parts A through C, we should first rewrite the expression as a power involving a radical.

49^(3/2)
49^(1/2 * 3)
(49^(1/2))^3

a^(1/2)=sqrt(a)

(sqrt(49))^3

Having rewritten the expression as a power involving a radical, it is now easier to calculate. The square root of 49 is the number you have to multiply by itself to obtain 49, which is 7.

(sqrt(49))^3
(sqrt(7^2))^3
7^3

Next we want to calculate 7^3, which is 7 multiplied by itself 3 times.

7^3

a^3=a* a* a

7* 7* 7
(7* 7)* 7
49* 7

Note that this expression is not very easy to calculate. However, if we rewrite 49 as 50-1 and distribute 7, we get easier numbers to work with.

49* 7
(50-1)7
3500-7
3493

e Like in Parts A through D, we should first rewrite the expression as a power involving a radical.

125^(4/3)
125^(1/3 * 4)
(125^(1/3))^4
(sqrt(125))^4

Having rewritten the expression as a power involving a radical, it is now easier to calculate. The third root of 125 is the number you have to multiply by itself three times to obtain 125, which is 5.

(sqrt(125))^4
(sqrt(5^3))^4
5^4

Next we want to calculate 5^4, which is 5 multiplied by itself 4 times.

5^4
5* 5* 5* 5
(5* 5)* (5* 5)
25* 25

Note that this expression is not very easy to calculate. However, if we rewrite 25 as 20+5 and expand the parentheses, we get easier numbers to work with.

25* 25
(20+5)(20+5)
(20+5)^2
20^2+2(20)(5)+5^2
â–¼
Simplify
400+2(20)(5)+25
400+200+25
625

f Notice that the exponent in this power can be simplfied to 3 by calculating the quotient.
100^(6/3)=100^2 To calculate this expression we have to multiply 100 by itself. 100^2=100* 100=10 000