2x-3/(x^2-x-42)-3/(x^2-11x+28)=2/(x-7)
x^2-x-42=0
D=1+4*42=168+1=169=13^2
x1=(1+13)/2=7
x2=(1-13)/2=-6
x^2-11x+28=0
D=121-4*28=9=3^2
x1=(3+11)/2=7
x2=(3-11)/2=-4
(2x-3)/((x-7)(x+6))-3/((x-7)(x+4))=2/(x-7)|*(x-7)(x+6)*(x+4)
(2x-3)*(x+4)-3(x+6)=2(x+6)(x+4)
2x^2+8x-3x-12-3x-18=2(x^2+4x+6x+24)
2x^2+2x-30=2x^2+20x+48
2x^2+2x-30-2x^2-20x-48=0
-18x-78=0
18x=-78
x=-78/18=-13/3=-4 1/3
