Please help me I promise I will mark brainliest, I need an answer asap!!!!!!!! please hurry!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! f(x) = 3x + 9, g(x) = 5x^2 Find (f + g)(x). A). -5x^2 + 3x + 9 B). Quantity three x plus 9 divided by five x squared. C). 15x^3 + 45x D). 5x^2 + 3x + 9