(x + a)(x + b)

[crackgmat007]

If x^2 + 3x + c = (x + a)(x + b) for all x, what is the value of c ?
(1) a = 1
(2) b = 2

OA - D Pls explain

[cramya]

In a quadratic equation

x^2+3x+c = (X+a) (x+b)

The factors are a and b (this means -a and -b are the roots of this quadratic)

3 is nothing but sum of the factors (a+b)
c is nothing but product of the factors(a*b)

Stmt I

a=1
a+b = 3
1+b=3
b=2

we can find c= a*b (1*2)

SUFF

Stmt II

b=2

We know a+b=3 and b=2 so a=1

c=a*b = 1*2 = 2

SUFF

Hope I dint miss something. I have explained in detail but once we get the concept we dont have to even waste time doing the above.

Let me know if u still hv questions.

D

[crackgmat007]

great explanation...i get it. tx much