36=12d is a proportional or Non-proportional? Explain

Let f(x) = 3 − x . find the average rate of change of f(x) from x = a to x = a + h and simplify your answer so that no single factor of h is left in the denominator.

What is the expression in factored form? 225x^2 - 144 a. 9(5x+4)^2 b. 9(5x-4)^2 c. 9(4x+5)(4x-5) d. 9(5x+4)(5x-4)

Which steps could be part of the process in algebraically solving the system of equations, y+5x=x^2+10 and y=4x-10