Question

Solve the quadratic equation by completing the square.

=+x2+18x760
First, choose the appropriate form and fill in the blanks with the correct numbers.
Then, solve the equation. Round your answer to the nearest hundredth.
If there is more than one solution, separate them with commas.

Answer 1

There is no "sign" in front of the 760 so we'll assume it is "+".
x2 +18x +760 = 0
Move "non-x" term to the right

x2 +18x = -760

Divide equation by the factor of "x" which is "1" so this doesn't have to be done.

• take the coefficient of X (which is 18)
• divide it by 2
• square that number
• then add it to both sides of the equation.

18 / 2 = 9
9^2 = 81

x2 +18x +81 = -760 +81
x2 +18x +81 = -679
Taking the square root if both sides:
(x+9)*(x+9) = 26.0576284416 1
x1 = -9 plus 26.058 i
x2 = -9 minus 26.058 i