Jamal left home and was driving to his brother's house in Charlotte at an average speed of 51 miles per hour. One hour later, his sister left from the same house and traveled at an average of 68 miles per hour to catch up with him. She traveled by the same roads as Jamal. How long did it take her to catch up?

(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.