Question

For all values of x, f(x) = 2x-3 and g(x) = x^2 + 1 a) Find fg(x) Simplify and give your answer in the form ax^2 + b b) Find gf(x).

Answer 1

fg(x) = 2x² - 1

gf(x) = 4x²-12x +10

Explanation:

Given the functions f(x) = 2x-3 and g(x) = x^2 + 1

a) f(g(x)) = f(x²+1)

f(x²+1) = 2(x²+1) -3

f(x²+1)= 2x²+2 -3

f(x²+1) = 2x² - 1

fg(x) = 2x² - 1

Hence function fg(x) is 2x² - 1

b) gf(x) = g(2x-3)

g(2x-3) = (2x-3)² + 1

g(2x-3) = (2x-3)(2x-3) + 1

g(2x-3) = 4x²-6x-6x+9 + 1

g(2x-3) = 4x²-12x +10

gf(x) = 4x²-12x +10