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Ann [662]
3 years ago
10

Find the zeros of y=x2-4x-9 by completing the square

Mathematics
1 answer:
Naya [18.7K]3 years ago
8 0

Answer:

x = 2 ± \sqrt{13}

Step-by-step explanation:

To find the zeros let y = 0, that is

x² - 4x - 9 = 0 ( add 9 to both sides )

x² - 4x = 9

To complete the square

add ( half the coefficient of the x- term )² to both sides

x² + 2(- 2) x + 4 = 9 + 4

(x - 2)² = 13 ← take the square root of both sides

x - 2 = ± \sqrt{13} ← add 2 to both sides

x = 2 ± \sqrt{13}

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