Question

If f(x) = 4x² - x + 1, then f(a + 1) equals

Answer 1

f(a + 1) = 4(a + 1)² - (a + 1) + 1 = 4a² + 8a + 5

Answer 2

f(a + 1) = 4a² + 7a + 4

Explanation:

f(x) = 4x² - x + 1 ← substitute x = a + 1 into f(x) , that is

f(a + 1)

= 4(a + 1)² - (a + 1) + 1 ← expand parenthesis using FOIL

= 4(a² + 2a + 1) - a - 1 + 1 ← distribute parenthesis by 4

= 4a² + 8a + 4 - a ← collect like terms

= 4a² + 7a + 4