fg(x) = 2x² +10x -28
Since this is an operation with functions. Let's multiply both functions and then check.
f(x) = x+7
g(x) =2x -4
f * g (x) = (x+7)(2x-4) Distribute the factors
fg(x) = 2x² -4x +14x -28
fg(x) = 2x² +10x -28
2) So the product of both functions, i.e. fg(x) = 2x² +10x -28