That is a quadratic equation. To find its square, think of two numbers that when multiplied, the answer would be the last term, constant 9 and if those two numbers are added, the answer would be the middle term, the constant 10 with variable x. These are positive integers 9 and 1, respectively.
(x² + 10 x + 9) = 0
= (x + 9 ) (x + 1)
Using the FOIL method to check, the square is equal to the quadratic equation.
