解方程（30－2x）（24－2x）x＝1040

(30 - 2x) (24 - 2x) x = 1040
(720 - 60 x - 48 x + 4 x^2) x = 1040
(4 x^2 - 108x + 720) x = 1040
4 x^3 - 108x^2 + 720 x - 1040 = 0
x^3 - 27 x^2 + 108 x - 260 =0
(x - 2) (x^2 - 25 x + 130) = 0
(x - 2 = 0) 或 (x^2 - 25 x + 130 = 0)
(x = 2) 或 x={-(-25)-[(-25)^2-4(1)(130)]^(-1/2)}/(2*1)
或 x={-(-25)-[(-25)^2-4(1)(130)]}/(2*1)
(x = 2) 或 {x = [25 - (105)^(-1/2)]/2 }
或 {x = [25 + (105)^(-1/2)]/2 }