How to write the expression for (f×g)(x)

Question

f(x)=x-1

g(x)=4x+3

Find (f×g)(x)=-3

Answer 1

Hi Jovy,

f(x)=x-1 First of all you need to know (f*g)(x) = f(x) * g(x)

g(x)=4x+3

(f×g)(x) = (x - 1) (4x + 3) = 4x^2 -4x +3x -3 = 4x^2 -x -3

For finding x when we have (f×g)(x)=-3

4x^2 -x -3 = -3

4x^2 -x = 0 -------> ( factor of x)

x( 4x -1 ) = 0 -------> x = 0 and 4x - 1 = 0------> x = 1/4

by x = 0 and x = 1/4 you will have (f×g)(x)=-3

I hope it is useful,

Minoo