Answer:
f(x) + g(x) = -9x³ - 14x² + 2x + 7
Explanation:
This notation (f + g)(x) just wants you to add the two functions; it's the same thing as writing f(x) + g(x).
f(x) = -6x² + 9x + 7
g(x) = -9x³ - 8x² - 7x
All you have to do now is combine like terms and simplify.
f(x) + g(x) = (-6x² + 9x + 7) + (-9x³ - 8x² - 7x)
f(x) + g(x) = -6x² + 9x + 7 + -9x³ - 8x² - 7x
f(x) + g(x) = -9x³ - 8x² - 6x² + 9x - 7x + 7
f(x) + g(x) = -9x³ - 14x² + 2x + 7