I think i saw this solved in an earlier post but I can't seem to find it...
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Its E =20
use (a+b)^2 = a^2 +b^2+2ab
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SQ. Roots
Source: Beat The GMAT — Problem Solving |
Sqrt(9+srq80) + sqt(9-sqrt80)}^2
This is (a+b)^2 = a^2 +b^2+2ab
[sqrt(9+sqrt80)]^2 +[sqrt(9-sqt 80)]^2 - 2*{sqrt(9+sqt80)*sqt(9-sqt80)
=> 9+sqt80 +9- sqt80 - 2
=20
I hope its clear ,its hard to explain without using proper symbols.
This is (a+b)^2 = a^2 +b^2+2ab
[sqrt(9+sqrt80)]^2 +[sqrt(9-sqt 80)]^2 - 2*{sqrt(9+sqt80)*sqt(9-sqt80)
=> 9+sqt80 +9- sqt80 - 2
=20
I hope its clear ,its hard to explain without using proper symbols.
Hi,
I think nycgrl has done some basic mistakes although answer quoted is correct.
It may be seen that 9+9-2=/20 but,
it would be 9+9+2Sqrt1=20
I think nycgrl has done some basic mistakes although answer quoted is correct.
It may be seen that 9+9-2=/20 but,
it would be 9+9+2Sqrt1=20
sqrt(9+sqrt(80)) * sqrt(9- sqrt(80)) =1 ?
= Sqrt (9^2 - [sqrt 80]^2); since it is (a+b)*(a-b)=a^2-b^2
= Sqrt(81-80)
=sqrt(1)
=1
= Sqrt (9^2 - [sqrt 80]^2); since it is (a+b)*(a-b)=a^2-b^2
= Sqrt(81-80)
=sqrt(1)
=1
