Let us assume that the quadratic function is f(x) such
that:
`f(x)= ax^2 + bx + c`
``
Given the points: (2, 6) ( -2, -2) and (1,1).
Since the
points are on the graph, then they satisfy the
equation.
Then we will substitute with each point in
f(x).
`f(2)= a(2^2) + b*2 + C
`
`==> 4a + 2b + C = 6
.......(1)`
`f(-2) = a(-2^2) + b*-2 + C
`
`==> 4a - 2b + C = -2
............(2)`
`f(1) = a(1^2) + b*1 +
C`
`==> a + b + C = 1
................(3)`
Now we will solve the
system.
First we will subtract (2) from
(1).
==> 4b = 8 ==> b=
2
Now we will subtract (3) from
(2).
==> 3a -3b =
-3
==> a - b= -1
But b=
2
==> a - 2 = -1 ==> a =
1
==> a+ b+ c =
1
==> 1 +2 + C =
2
==> C = -2
Then the
function is:
`f(x)= x^2 + 2x -2
`
``
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