x 2-9x 0, x 2 + 9x + 18 0, x 2 9x 20 0 completing the square, if x 0 then sqrt 4x + sqrt 9x 2, x 3 3x 2-9x 5 0, x 2 - 9x + 20 0, x 2 + 9x + 20 0, x 2 9x 0 solve, x 2 9x 14 0
x 2-9x 0. There are any references about x 2-9x 0 in here. you can look below.