(1/6x-45)-(1/6x+45)-(3x/45^2-9x^2)
去括号得到：
原式=1/6x-45-1/6x-45-3x/45^2+9x^2
=9x^2-3x/45^2
=3x(3x-1/45^2)
(1/6x-45)-(1/6x+45)-(3x/45^2-9x^2)
(1/6x-45)-(1/6x+45)-(3x/45^2-9x^2)
去括号得到：
原式=1/6x-45-1/6x-45-3x/45^2+9x^2
=9x^2-3x/45^2
=3x(3x-1/45^2)