Question

http://prntscr.com/8ooofr

Answer 1

@dan815

Answer 2

look. your parabola points down. so what do you think will be the vertex of the parabola: maximum or minimum value of function?

Answer 3

maximum?

Answer 4

yep.

Answer 5

do you know why parabola points down?

Answer 6

because its negative?

Answer 7

here is the standard form of the quadratic function:
\[y=ax^2+bx+c\]
if a<0, the parabola points down, if a>0 parabola point up.