Which of the following could be the equation for a parabola that opens down with vertex (-11, -28)

Question

A. Y=5(x+28)^2 -11

B. X=5(y+11)^2 -28

C.y=-5(x+11)^2 -28

D.x=-5(y+28)^2 -11

Answer 1

Okay think about what you know about translations and transformations of parent functions. In this case, the parent function is x². So what now?

 

First, the problem states that the parabola opens DOWN. This means that you should look for a negative leading coefficient. This narrows your options down to C or D. (-5 is the leading coefficient)

 

Now starting with the x², the vertex would be at (0,0), but in this problem it is at (-11,-28). That means it was TRANSLATED 11 spots in the negative x-direction and 28 spots in the negative y-direction.

 

Look at your options, when a number is being added directly unto the x variable, such as in answer C, it moves in the negative x-direction. This tells you that C has to be your answer.

 

I hope that helps!