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Re-write the quadratic function in vertex form: y=8x^2−144x+640

User Boune
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Answer:

y = 8(x - 9)² - 8

Explanation:

A quadratic function in vertex form is

y = a(x - h)² + k

(h, k ) are the coordinates of the vertex and a is a multiplier

given

y = 8x² - 144x + 640 ← in standard form

using the method of completing the square to obtain vertex form

Before applying the method we require the coefficient of the x² term to be 1

factor out a common factor of 8 from the first 2 terms

y = 8(x² - 18x) + 640

add/subtract ( half the coefficient of the x- term)² to x² - 18x

y = 8(x² + 2(- 9)x + 81 - 81) + 640

= 8(x - 9)² + 8(- 81) + 640

= 8(x - 9)² - 648 + 640

= 8(x - 9)² - 8 ← in vertex form

User Roz
by
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