College Algebra f(x) function

Question

If f (x)=3x^2-1, find f (a+b)

Please help me!

Answer 1

Hello, thank you for taking the time to post your question!

In order to evaluate this one you want to plug in x = a + b into the function

f(a + b) = 3(a + b)^2 – 1

=3(a^2 + 2ab + b^2) – 1

=3a^2 + 6ab + 3b^2 - 1

I hope that helps you get moving in a better direction on this type of question! Feel free to reach out if you have any additional questions beyond that :)

Answer 2

f(a + b) means to evaluate f(x) when  x = a + b

 

You are basically making the substitution for x.  Then evaluating.

 

f(a + b) = 3(a + b)² - 1

 

 

Now just expand and simplify.