Question

Find a quadratic model for the set of values: (-2, -20), (0,-4), (4,-20). Show your work

Answer 1

What is the quadratic model?

Answer 2

Let the quadratic model be
\[y=ax^2+bx+c~ ..... (1)\]
when x=0,y=-4
-4=0+0+c
c=-4
\[when~x=-2,y=-20\]
\[-20=4a-2b-4\]
when x=4,y=-20
-20=16a+4b-4
16a+4b-4=4a-2b-4
12a=-6b
-2a=b
-20=4a-2b-4
-16=4a-2(-2a)
8a=-16
a=-2
b=-2*-2=4
y=-2x^2+4x-4