Помогите решить уравнение (2-7x) (5+4x) = 0

(2-7x) (5+4x) = 0

10+8x-35x-28x^2=0

-28x^2-27+10=0

D = 729-4 * (-28) * 10 = 729+1120 = 1849

x1 = 27-43 / - 56 = - 16/-56 = 16/56 = 8/28 / = 4/14 / 2/7

x2 = 27+43 / - 56 = 70/-56 = - 5/4 = - 1.25

или

2-7x = 0

-7x = - 2

x = 2/7

5+4x = 0

4x = - 5

x = - 5/4

x = - 1.25