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Exponents, Radicals, & More [#permalink]
16 Nov 2009, 20:53

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Difficulty:

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Question Stats:

100% (01:39) correct
0% (00:00) wrong based on 5 sessions

(sqrt(9 +sqrt80) + sqrt(9-sqrt80))^2 The square root of the sum of 9 and the square root of 80 plus the square root difference (so subtraction) between 9 and the square root of 80 (so the 9’s are under one radical (initial square root) and the 80’s are under 2 radicals. a) 1 b) 9 – 4(5)^1/2 c) 14 d) 18 e) 20

Last edited by chicagocubsrule on 17 Nov 2009, 15:10, edited 1 time in total.

Re: Exponents, Radicals, & More [#permalink]
16 Nov 2009, 21:21

chicagocubsrule wrote:

((9^(1/2) +80^(1/4)) +(9^(1/2) – 80^(1/4)) ^2 The square root of the sum of 9 and the square root of 80 plus the square root difference (so subtraction) between 9 and the square root of 80 (so the 9’s are under one radical (initial square root) and the 80’s are under 2 radicals. a) 1 b) 9 – 4(5)^1/2 c) 14 d) 18 e) 20

I keep getting 36..are you sure this is correct?

I double-checked with google calculator and it too got 36

Re: Exponents, Radicals, & More [#permalink]
17 Nov 2009, 06:23

chicagocubsrule wrote:

((9^(1/2) +80^(1/4)) +(9^(1/2) – 80^(1/4)) ^2 The square root of the sum of 9 and the square root of 80 plus the square root difference (so subtraction) between 9 and the square root of 80 (so the 9’s are under one radical (initial square root) and the 80’s are under 2 radicals. a) 1 b) 9 – 4(5)^1/2 c) 14 d) 18 e) 20

answer 20

but question should read (sqrt(9 +sqrt80) + sqrt(9-sqrt80))^2

Re: Exponents, Radicals, & More [#permalink]
17 Nov 2009, 15:09

lagomez wrote:

chicagocubsrule wrote:

((9^(1/2) +80^(1/4)) +(9^(1/2) – 80^(1/4)) ^2 The square root of the sum of 9 and the square root of 80 plus the square root difference (so subtraction) between 9 and the square root of 80 (so the 9’s are under one radical (initial square root) and the 80’s are under 2 radicals. a) 1 b) 9 – 4(5)^1/2 c) 14 d) 18 e) 20

answer 20

but question should read (sqrt(9 +sqrt80) + sqrt(9-sqrt80))^2

my mistake (I've edited my original post)...answer is 20...can you please explain?

Re: Exponents, Radicals, & More [#permalink]
17 Nov 2009, 15:42

chicagocubsrule wrote:

lagomez wrote:

chicagocubsrule wrote:

((9^(1/2) +80^(1/4)) +(9^(1/2) – 80^(1/4)) ^2 The square root of the sum of 9 and the square root of 80 plus the square root difference (so subtraction) between 9 and the square root of 80 (so the 9’s are under one radical (initial square root) and the 80’s are under 2 radicals. a) 1 b) 9 – 4(5)^1/2 c) 14 d) 18 e) 20

answer 20

but question should read (sqrt(9 +sqrt80) + sqrt(9-sqrt80))^2

think of (a+b)^2 = a^2 + 2ab + b^2

let's say a = sqrt(9 + sqrt80) so that squared = 9 + sqrt 80

Re: Exponents, Radicals, & More [#permalink]
17 Nov 2009, 15:51

chicagocubsrule wrote:

(sqrt(9 +sqrt80) + sqrt(9-sqrt80))^2 The square root of the sum of 9 and the square root of 80 plus the square root difference (so subtraction) between 9 and the square root of 80 (so the 9’s are under one radical (initial square root) and the 80’s are under 2 radicals. a) 1 b) 9 – 4(5)^1/2 c) 14 d) 18 e) 20