Question

Complete the square x^2+18x+_

Answer 1

x^2 + 18x + 81 complete's the square.

Explanation:

y = [x^2 + 18x + (18/2)^2 ] - (18/2)^2

y = [x^2 + 18x + 81] - 81

y = (x + 9)^2 - 81 This is just to make the completion of the square accurate.

You can't just add something to an expression. You have to balance it out.