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What is the range of y = x² - 8x + 4?

User AlexO
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Answer: [-12 , ∞)

Explanation:

To find the range of a parabola you would like the equation in the form y=ax²+bx+c, which is how it is given, to find the vertex.

From there you can use the equation x₁= -b/2a to find the x coordinate.

-(-8)/2(1) = 4.

Then you just plug the x₁ value into the original function to find the y-value.

y₁=(4)²-8(4)+4=16-32+4=-12

So we can conclude the vertex is (4,-12) and because the equation is a parabola that looks like a U, the y values or range, will start and -12 and go up to infinity. -12≤x or in interval notation [-12,∞).

User Cmcquillan
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