Question 30642: I need to know the vertex and how to graph it. Thank you.
y=-2(x-3)(x+1)
Answer by Fermat(136)   (Show Source):
You can put this solution on YOUR website! A parabola which has its vertex at the point (a,b) can be written as,
(y-b) = (x-a)²
or,
(y-b) = C(x-a)²
if it is scaled.
You have y=-2(x-3)(x+1), so convert it to the above form.
y=-2(x-3)(x+1)
expand it,
y = -2(x² - 2x - 3)
y = -2(x² - 2x + 1 - 4)
y = -2{(x - 1)² - 4}
y = -2(x-1)² + 8
(y-8) = -2(x-1)²
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Here the parabola has a scaling factor, 2, which means it is slimmer, and it has a change of sign, the minus sign, hence it is upside down.
The vertex is at the point (a,b) = (1,8)
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