QUADRATICS: Find vertex from factored form without changing the ...

[camila]

how do I find the vertex of this without changing the form?

f(x)= -0.7(1.1-x)(3.2+x)

[Jones]

1) find the roots:
x= 1.1
x=-3.2

The axis of symmetry is x= (1.1 - 3.2) /2= -1.05
So the x coordinate of the vertex is -1.05

Sub x= -2.1 into f(x), and you'll get the y coordinate of the vertex.


So the vertex is (-1.05, f(-1.05) )

I think you can continue from there....

[Hawke]

the roots are 1.1 , - 3.2

so the vertex must be x = [1.1 + (-3.2)] / 2 = - 1.05 ( in the middle)