Could someone please help me with this math question?

Which quadratic equation fits the data in the table?
enter image source here
A) y = x² − 7x − 1

B) y = −x² + 7x + 1

C) y = x² −7x + 1

D) y = x² + 7x + 1

1 Answer
Feb 2, 2018

Choice D works.

Explanation:

The table you have with x and y values should make the correct equation true. Remember the x and y values fit into each coordinate pair, or ordered pair, like this: (x,y).
I looked first at the ordered pair (0,1). If you put 0 in for x in equation A, you get y=0^2-7(0)-1 = 0-0-1=-1. But in the ordered pair (0,1), x=0 and y=1. When you plugged 0 in for x, you got y=-1, and that's not right.
Any of the others would give you y=1 when you plug in x=0.
Another easy point to look at is (1,9). Out of the next three choices, we want to see if we get y=9 when we plug 1 in for x:

For B. we get: -(1^2)+7(1)+1=-1+8+1=8, and 8!=9.

Equation C: (1)^2-7(1)+1=-5, and -5!=9.

Try D: (1)^2+7(1)+1=9 and yes! 9=9

So we don't need to try any other coordinate pairs; all of them should work, and these two don't work in equations A,B, or C.
I hope that helps!