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square root + square root}^2 a. 1 b. 9- (4 square root 5) c.

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Manager
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square root + square root}^2 a. 1 b. 9- (4 square root 5) c. [#permalink]

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20 Apr 2006, 16:52
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

{square root[9 + (square root 80)] + square root[9 - (square root 80)]}^2

a. 1

b. 9- (4 square root 5)

c. 18 - (4 square root 5)

d. 18

e. 20

(I hope the equation is clear. 9+ square root 80 is inside a square root. 9 - square root 80 is inside a square root.)
Senior Manager
Joined: 15 Mar 2005
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20 Apr 2006, 16:59
jlui4477 wrote:
{square root[9 + (square root 80)] + square root[9 - (square root 80)]}^2

a. 1

b. 9- (4 square root 5)

c. 18 - (4 square root 5)

d. 18

e. 20

(I hope the equation is clear. 9+ square root 80 is inside a square root. 9 - square root 80 is inside a square root.)

The eqn becomes
9 + sqrt(80) + 9 - sqrt (80) + 2 sqrt(9 + sqrt(80)) * sqrt(9 + sqrt(80))
= 18 + 2 sqrt(81 - sqrt(80)^2)
= 18 + 2 sqrt (1) = 20
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20 Apr 2006, 20:17
jlui4477 wrote:
{square root[9 + (square root 80)] + square root[9 - (square root 80)]}^2

a. 1
b. 9- (4 square root 5)
c. 18 - (4 square root 5)
d. 18
e. 20
(I hope the equation is clear. 9+ square root 80 is inside a square root. 9 - square root 80 is inside a square root.)

agree with E.

is not it possible to make available special characters such as sqrt, infinite, superscript, subscript or any other characters as required on this window? this is because it has been really confusing and time consuming to figure out the peoblems and their solutions....

hope you take my suggestions positively..

prof..
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20 Apr 2006, 21:06
I'm not following. What is your first step?

The eqn becomes
9 + sqrt(80) + 9 - sqrt (80) + 2 sqrt(9 + sqrt(80)) * sqrt(9 + sqrt(80))
= 18 + 2 sqrt(81 - sqrt(80)^2)
= 18 + 2 sqrt (1) = 20
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20 Apr 2006, 21:31
jlui4477 wrote:
I'm not following. What is your first step?

The eqn becomes
9 + sqrt(80) + 9 - sqrt (80) + 2 sqrt(9 + sqrt(80)) * sqrt(9 + sqrt(80))
= 18 + 2 sqrt(81 - sqrt(80)^2)
= 18 + 2 sqrt (1) = 20

I guess he used square of the sum formula
(a+b)^2=a^2+2ab+b^2
Hope this helps
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20 Apr 2006, 21:31
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