Tìm x biết

Tìm x bt:
a)(x-4).(x+5)-(x-1).(x-2)=7
b)5.(x-3).(x-7)-(5x+1).(x-2)=8
c)5x.(12x-7)-(15x+1).(4x-1)=-23
d)12x^2-4x.(3x+1)=x-15