Is number 5 a function or not a function and why?

This is so harddd! solve. 1 + 1 = solve 4 + 4 = solve 3 x 3

Isabel graphed the following system of equations. 2x – y = 6 y = -3x + 4 she came up with the solution (2,-2). what were the 3 steps she did to get that solution? (make sure they are in the correct order)

Rewrite the following quadratic functions in intercept or factored form. show your work. f(x) = 3x^2 - 12