Tricky DS question..

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Tricky DS question..

by mav800rick » Thu May 29, 2008 3:33 pm
If x2 + 3x + c = (x + a)(x + b) for all x, what is the value of c ?
(1) a = 1
(2) b = 2

OA is D. Any ideas how?

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by chidcguy » Thu May 29, 2008 4:47 pm
x ^ 2 + 3x + C = (x+a) (x+b) = x^2 + (a+b) x + ab

a=1 means b=2.

because the coefficient of x is nothing but sum of a and b, C is the product of a and b a+b =3 and C=ab

b=2 means a=1