17,28,31,36,43,21,23,27,14,21,18,21 what is the median of these numbers

(a) x intercepts: -6 and 2

you can obtain these by solving the equation 0=x^2 +4x-12 using your favorite quadratic formula. but it is easy to verify -6 and 2 indeed satisfy this equation.

(b) y intercept: -12

this is obtained by setting x=0: 0^2+4*0-12 = -12

(c) the minimum value is: -16 (this is the vertex)

you can get the vertex by rewriting the equation into the form:

there is no global or local maximum as the function goes to infinity, so only in the limit sense: +infinity.

well it says right there your brother is 13; "your age". so lets keep it simple. you are 13 years old and there is no way to put this into any kind of equation without wanting to tear your hair out. who came up with this?