A) общий знаменатель 60m²n²
(3m(4n -m) -4n(3m+n)) /60m²n² =
=(12mn -3m² -12mn -4n²) /60m²n² =
=(-3m² -4n²) /60m²n²
b) (8 +(x -2)(x²+2x+4)) /(x -2) =
=(8 +x^3 -8) /(x -2) =x^3/(x -2)
в) ((x +y)(x -4y) -(x -y)(x+4y)) /6x(x-y)(x+y) =
=(x² -3xy -4y² -x² -3xy +4y²) /6x(x² -y²) =
=(-6xy) /6x(x² -y²) = -y/(x² -y²)
г) (b+3)/9(b-3) - (b-1)/b(b-3) =
=(b(b+3) -9(b -1)) /9b(b -3) =
=(b² +3b -9b +9) /9b(b -3) =
=(b² -6b +9) /9b(b -3) =(b -3)² /9b(b -3) =
=(b -3) /9b