Given $f(x)=2x^2−4$ and $g(x)=5x+3$, find the value of each expression below.

1. $f(a)$ 

2. $f(3a)$ 

3. $f(a+b)$ 

   Answer (c):

   $f(a+b)=2a^2+4ab+2b^2−4$

4. $f(x+7)$ 

5. $f(5x+3)$ 

6. $g(f(x))$ 

   Answer (f):

   $f(g(x))=10x^2−17$