Question

How do you evaluate `f( 15)` if `f(x)= x ^ { 3} - 6x + 4`?

Answer 1

See a solution process below:

Explanation:

To evaluate `f(15)` you need to substitute `color(red)(15)` for each occurrence of `color(red)(x)` in `f(x)`:

`f(color(red)(x)) = color(red)(x)^3 - 6color(red)(x) + 4` becomes:

`f(color(red)(15)) = color(red)(15)^3 - (6 xx color(red)(15)) + 4`

`f(color(red)(15)) = 3375 - 90 + 4`

`f(color(red)(15)) = 3285 + 4`

`f(color(red)(15)) = 3289`