Monday, December 1, 2014

Write a quadratic function in standard form whose graph passes through the given points : (2,6) (-2,-2) (1,1)Help !

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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