Anonymous

How to solve for x by completing the square, to the nearest 10th x^2-8x-18=0? Show your work!

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John McCann Profile
John McCann answered

X^2 - 8X - 18 = 0

X^2 - 8X = 18

take the coefficient of the X term,half it,square it and add it to both sides

X^2 - 8X + 16 = 18 + 16

X^2 - 8X + 16 = 34

factor the left side

(X - 4)^2 = 34

X - 4 = (+/-) sqrt(34)

X = (+/-)  sqrt(34) + 4

This is the exact answer. For the HS answer..,

X = 9.8

X = - 1.8

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