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by sanju09 » Sat Jun 19, 2010 2:09 am
If x + y = √22 and x - y = √10, then x y =
(A) 3
(B) 12
(C) √22 √10
(D) 16
(E) 55
The mind is everything. What you think you become. -Lord Buddha



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by kvcpk » Sat Jun 19, 2010 2:16 am
sanju09 wrote:If x + y = √22 and x - y = √10, then x y =
(A) 3
(B) 12
(C) √22 √10
(D) 16
(E) 55
(x+y)^2 - (x-y)^2 = 4xy
so, 22-10 = 4xy
12 = 4xy
xy =3

A
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by sanju09 » Sat Jun 19, 2010 2:19 am
kvcpk wrote:
sanju09 wrote:If x + y = √22 and x - y = √10, then x y =
(A) 3
(B) 12
(C) √22 √10
(D) 16
(E) 55
(x+y)^2 - (x-y)^2 = 4xy
so, 22-10 = 4xy
12 = 4xy
xy =3

A
good one
The mind is everything. What you think you become. -Lord Buddha



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The Princeton Review - Manya Abroad
Lucknow-226001

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by amising6 » Sat Jun 19, 2010 2:28 am
sanju09 wrote:If x + y = √22 and x - y = √10, then x y =
(A) 3
(B) 12
(C) √22 √10
(D) 16
(E) 55
squareing both side you will get x^2+y^2+2xy=22 equation 1
x^2+y^2-2xy=10 equation 2
eq 1 -eq2
4xy=12
xy =3
Ideation without execution is delusion
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