Mark the correct alternative in the following:
If f : R → R and g : R → R are defined by f(x) = 2x + 3 and g(x) = x2 + 7, then the values of x such that g(f (x)) = 8 are
g(f(x))=8
(f(x))2+7=8
(2x+3)2=1
4x2+12x+9=1
4 x2+12x+8=0
x2+3x+2=0
(x+1)(x+2)=0
x+1=0 or x+2=0
x=-1 or x=-2
Option C is correct..