Pre-Calculus question including parabolas?
Write y = -2x^2 + x + 1 in vertex form.
This is my work:
Y = a(x - h)^2 + k
Vertex: -b/2a = -1/2(-2) = -1/-4 = 1/4
Then I plugged it in to the equation.
Y = -2(1/4)^2 + 4 + 1
Y = -2 (1/16) + 4 + 1
Y = -1/8 + 4 + 1
Y = 39/8 or 4.785
Vertex: (h,k) = (1/4,39/8)
Answer: y = -2 (X - 1/4)^2 + 39/8
Is this correct? If not, can you please show work & explain?
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Looks like you're doing it right, except that you made a mistake plugging in the vertex. Use x = 1/4 rather than x = 4:
y = -2(1/4)^2 + 1/4 + 1 = -1/8 + 1/4 + 1 = 1 1/8 = 9/8
Vertex: (1/4, 9/8)
Answer: y = -2(x - 1/4)^2 + 9/8
Check: y = -2(x^2 - 1/2 x + 1/16) + 9/8 = -2x^2 + x - 1/8 + 9/8 = -2x^2 + x + 1
The answer checks. Your work was good except for that one mistake.