Consider the functions f(x) = 2x + 1 and g(x) = x^2 − 10. What is the value of (f + g)(−2)

(f + g)(x) = x^2 + 2x - 9
(f + g)(-2) = 4 - 4 - 9 = -9

Problems like these (compositions of functions) are really quite simple.
f(x)=2x+1
g(x)=x²-10
So (f+g)(x) means you add the two functions. So (f+g)(x)=2x+1+x²-10=x²+2x-9
So, (f+g)(-2)=(-2)²+2(-2)-9=4-4-9=-9
You could also simply find f(-2) and add that to g(-2). (-3-9).