I hope this helps you
(fog)(5)=f (g (5))=?
x= 5 g (5)=-4.5+3=-20+3=-17
f (g(5))=f (-17)=-2. (-17)-7
f (-17)=34-7
f (-17)=27
Step 1. Find the Greatest Common Factor (GCF)
GCF = 7x^2
Step 2. Factor out the GCF (Write the GCF first. Then, in parentheses, divide each term by the GCF.)
7x^2(14x^4/7x^2 + 35x^2/7x^2)
Step 3. Simplify each term in parentheses
7x^2(2x^2 + 5)

is undefined where the denominator is zero. The domain is all values of x for which the function is defined.
The domain of f(x) is all real numbers except 13.