How do you work out this problem using completing the square x2 - 4x - 80 = 0

A value that satisfies this equation is called a root, zero or solution of the equation! We have three ... Solve each by factoring. 1) x2 + 4x - 5 = 0 ... Follow the explanation and sample problem to review completing the square.

x^2 - 4x = 80

x^2 - 4x + 4 = 80 + 4 (Divide b, which is 4, by 2 and square it.)

x^2 - 4x + 4 = 84

sqrt (x + 2) ^2 = sqrt (84)

x + 2 = plus or minus sqrt (84)

Subtract 2 from both sides

x = - 2 plus or minus sqrt (84)