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How do you solve #x^2 - 18x = 19# by completing the square?

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1 Answer

Jul 13, 2015

Solve: #y = x^2 - 18x - 19 = 0#

Explanation:

Since (a - b + c = 0), use the shortcut. The 2 real roots are: (- 1) and (-c/a = 19).

Solving by completing the squares

#x^2 - 18x + 81 = 19 + 81 = 100#
#(x - 9)^2 = 100# --> #x - 9 = +- 10#
#x = 9 +- 10# --> x = - 1 and x = 19.

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