(7x+3)*(3-7x)-9=x*(6-x)

(7x+3)*(3-7x)-9=x*(6-x)
(3+7x)*(3-7x) = 9-49x²
9-49х²-9 = 6х-x²
-49х²+x² -6x = 0
-48x²-6x = 0
6x(8x+1) = 0
6x = 0
 x₁ = 0

8x+1 = 0
8x = -1
x₂ = -1/8 = -0.125