Question

Find a quadratic function to model the values in the table. Predict the value of y for x = 4.

X|Y
-1|-3
0|-2
3|-35

Answer 1

the constant must be \(-2\) so you have
\[y=ax^2+bx-2\] as a start
now we can set up a couple equations in \(a\) and \(b\)

Answer 2

let \(x=-1\) you get
\[a-b-2=-3\] or\[a-b=-1\]

Answer 3

let \(x=3\) you get \[9a+3b-2=-35\] or \[9a+3b=-33\]

Answer 4

solve the system
\[a-b=-1\]\[9a+3b=-33\] to get your answer

Answer 5

multiply first equation by 3, add it to the second get \[12a=-36\] so \(a=-3\)
therefore \(b=-2\) and you get
\[y=-3x^2-2b-2\]

Answer 6

oops
\[y=-3a^2-2x-2\]

Answer 7

so it would be y=-3a^2-2x-2;-58

Answer 8

@satellite73

Answer 9

yes for the first one

Answer 10

it would be
\[y=-3x^2-2x-2\] with an \(x\) not an \(a\)

Answer 11

thanks so much. i've been working on this thing all weekend....

Answer 12

wait so 4 is going to be -56?

Answer 13

@satellite73