Function question: What do I do when f(x) has a sum inside, like f(x+3)?

[Pliniao]

what do i do when there is a sum inside the parentheses?

example: If f(x) = x^2 - 3x, the answer of f(x+3) - f(x) is equal to...
what do i do about that x+3?

 

[Steven G]

Regardless of what is in the parentheses you plug it in for x
For example: If f(x) = x^3 -6x, then f(xy+z) = (xy+z)^3 - 6(xy+z).
You need to be able to in words what the function x. In my example f cubes what is in the parentheses and then subtract 6 times what is in the parentheses.

 

[Steven G]

what do i do when there is a sum inside the parentheses?

example: If f(x) = x^2 - 3x, the answer of f(x+3) - f(x) is equal to...
what do i do about that x+3?

You square it and then subtract 3 times it