Which of the following quadratic functions has a graph that opens downward?

check all that apply.

a. y=2x-x^2
b. y= 1/3x^2-8x-13
c. y=2/3x^2-13x+5
d. y= -(3+x^2)

The answers are a) y=2x-x^2 and d) y=-(3+x^2) and in the attached file are the graphs.

Step-by-step explanation:

Quadratic equations are those where the exponent of the unknown term is squared, that is, the unknown is elevated to exponent 2. They have the general form of a trinomial:

ax2 + bx + c = 0

where a, b and c are real numbers and are called coefficients. Thus, a is the coefficient of x2, b is the term or coefficient of x and c is the independent term.

5

step-by-step explanation: