How do you solve x^2 - 18x = 19x2−18x=19 by completing the square?

1 Answer
Nghi N.
Jul 13, 2015

Solve: y = x^2 - 18x - 19 = 0y=x2−18x−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 = 100x2−18x+81=19+81=100
(x - 9)^2 = 100(x−9)2=100 --> x - 9 = +- 10x−9=±10
x = 9 +- 10x=9±10 --> x = - 1 and x = 19.

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