(a+b)^2=a^2+b^2+2ab
we need to find out a^2+b^2= (a+b)^2-2ab
now from stem 1
we have a+b=4...in sufficient (we need value of ab also)
from stem 2 we have ab = 1 (by taking a on other side) ...........but in 2 we dont know about a+b
together they suffice
a^2+b^2= (a+b)^2-2ab
== 4^2-2*1
== 14
answer C (both necessary)
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Source: Beat The GMAT — Data Sufficiency |
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(1) is NOT SUFFICIENT as we don't know the value of b.
(2) is NOT SUFFICIENT as we don't know the value of a.
Combining, a = 4 - 1/a or a^2 - 4a + 1 = 0, which is quadratic in a.
a = 2 + √3, 2 - √3 and so b = 1/(2 + √3), 1/(2 - √3)
Putting these values we get the value of a^2+b^2
The correct answer is (C).
(2) is NOT SUFFICIENT as we don't know the value of a.
Combining, a = 4 - 1/a or a^2 - 4a + 1 = 0, which is quadratic in a.
a = 2 + √3, 2 - √3 and so b = 1/(2 + √3), 1/(2 - √3)
Putting these values we get the value of a^2+b^2
The correct answer is (C).
Rahul Lakhani
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Gurome, Inc.
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On MBA sabbatical (at ISB) for 2011-12 - will stay active as time permits
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Quant Expert
Gurome, Inc.
https://www.GuroMe.com
On MBA sabbatical (at ISB) for 2011-12 - will stay active as time permits
1-800-566-4043 (USA)
+91-99201 32411 (India)
