Question

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

Answer 1

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.