Question

If f(x) =x^2-x , then evaluate f(a-4)

Answer 1

Explanation:

'x' shows up 3 times in f(x) =x^2-x. To evaluate f(a - 4), replace each instance of 'x' with 'a - 4:'

f(a - 4) = (a - 4)^2 - (a - 4)

This result could be left as is, or it could be expanded:

f(a - 4) = a^2 - 8a + 16 - a + 4, or

f(a - 4) = a^2 - 9a + 20

Answer 2

`→ \: { \tt{f(x) = {x}^(2) - x }}`

• when f(x) is f(a-4), x is (a - 4):

`→ \: { \tt{f(a - 4) = {(a - 4)}^(2) - a}}`

• Expand the bracket, from quadratic equation rules:

`{ \boxed{ \bf{ {(a - b)}^(2) = {a}^(2) - 2ab + {b}^(2) }}}`

• therefore:

`→ \: { \tt{f(a - 4) = ( {a}^(2) - 8a + 16) - a}} \\ \\ → \: { \boxed{ \tt{f(a - 4) = {a}^(2) - 9a + 16}}}`