# Thread: expanding and simplifying a function to determine if it is linear or quadratic

1. ## expanding and simplifying a function to determine if it is linear or quadratic

I haven't done this in a while so I can't remember how to do everything, just when I thought I had it figured out, my answer did not match with the correct one. Here's the question:
6.State the degree of each function, and identify which functions are linear and which are quadratic.
b) m(x) = -x^2 + (x +3)^2

m (x) = -x^2 + (x + 3)(x + 3)
= -x^2 + x(x + 3) + 3(x + 3)
= -x^2 + x^2 + 3x + 3x +9
= 6x + 9

The degree is 1 because the highest exponent of x is 1. The function is linear

Apparently the answer is : the degree is 2 and the function is quadratic. I know I must have not done at least one thing right here... hopefully someone can tell me what that is.