Question

Which of the following quadratic functions has a graph that opens downward? A.y= 3/2x^2 -3x+15 B.y= 5/2x-3x^2 C.y= 3x^2-x-1 D.y= -(2x^2-1)

Answer 1

it says if

ax^2+bx+c=0

a<0

answer is D because, there is (-) near of x^2