# Math Help - Combinations Of Functions

1. ## Combinations Of Functions

(f)(g) (x) f(x)= -x^2+2 g(x)=3x^2+2x-1
I need to multiply these together
I know its setup as follows
(x^2+2)(3x^2+2x-1)
I know x^2 has to be multiplied to everything in the "( )" first.
I get -3x^4 but then the next thing that needs to be done is multiply -x^2 by 2x. However, according to my calculus teacher, u cant multiply a number that is squared by a number thats not, do I simply bring it down as -x^2(2x) and continue.. if so what is the final result?

2. You can multiply any two numbers together, regardless of powers. You just add the exponents when you do so.

But you can't ADD two numbers with different exponents together.

That may have been what your teacher was saying.

3. (-x^2+2)(3x^2+2x-1)
= -3x^4 -2x^3 + 7x^2 +4x -2

4. Originally Posted by KeiaBlake
(f)(g) (x) f(x)= -x^2+2 g(x)=3x^2+2x-1
I need to multiply these together
I know its setup as follows
(x^2+2)(3x^2+2x-1)
I know x^2 has to be multiplied to everything in the "( )" first.
I get -3x^4 but then the next thing that needs to be done is multiply -x^2 by 2x. However, according to my calculus teacher, u cant multiply a number that is squared by a number thats not, do I simply bring it down as -x^2(2x) and continue.. if so what is the final result?
you were not listening properly. $-x^2(2x) = -2x^3$

but yes, you are right. take each term in the first pair of brackets and multiply everything in the second set.