SOLUTION: I really need help on vertex forms and standard form parabolas. I understand how to get the vertex but I don't understand when a problem is like this: (x+1)(x-3) and (x+3)^2 -1

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: I really need help on vertex forms and standard form parabolas. I understand how to get the vertex but I don't understand when a problem is like this: (x+1)(x-3) and (x+3)^2 -1      Log On


   

Question 1021931: I really need help on vertex forms and standard form parabolas. I understand how to get the vertex but I don't understand when a problem is like this: (x+1)(x-3) and (x+3)^2 -1
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
I really need help on vertex forms and standard form parabolas. I understand how to get the vertex but I don't understand when a problem is like this:
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y = (x+1)(x-3)
y = x^2 - 2x - 3
a = 1 ; b = -2 ; c = -3
Vertex occurs at x = -b/(2a) = 2/(2*1) = 1
--------
f(1) = 1^2 -2*1 - 3 = -4
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Vertex:: (1,-4)
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y = (x+3)^2 -1
y = x^2 + 6x + 8
a = 1 ; b = 6 ; c = 8
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Vertex at x = -b/(2a) = -6/(2*1) = -3
f(-3) = (-3+3)^2 - 1 = -1
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Vertex:: (-3,-1)
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Cheers,
Stan H.
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