(x-17)=0    или (x+2x-40)=0 

х=17              3х=40

                       х=40/3

(x-17)(x+2x-40)=0

x^2+2x^2-40x-17x-34x+680=0

3x^2-91x+680=0 

 3x2 - 91x + 680 = 0
D = b2 - 4ac
D = 8281 - 8160 = 121 = 11^2

x1,2 = -b ± √D/2a
x1 = 91 + 11/6 = 102/6 = 17
x2 = 91 - 11/6 = 80/6 = 40/3
Ответ: x1 = 17 ; x2 = 40/3