Tìm x, biết (x - 6) (x - 7) - (x + 5)^2 - 2x = x - 9

Bài 2 : Tìm x, biết :
$$\begin{gathered} a, (x-6)(x-7)-{(x+5)}^2-2x=x-9 \\ b, 25(x-4)(x+4)-{(1-5x)}^2+3=2(x-4) \\ c, {(x+1)}^2-2(x+1)(2-3x)+{(2-3x)}^2=0 \end{gathered}$$