а) (7x-3y)/(2x-y) - (2y-3x)/(2x-y) = (7x-3y-2y+3x)/(2x-y) = (10x-5y)/(2x-y) = 5(2x-y)/(2x-y) = 5.
б) (4x-3y)/(6x-3y) + (2x-y)/(2x+5y) = (4x-3y)/(3(2x-y)) + (2x-y)/(2(x+5y)) = (4x-3y)/(3(2x-y)) + (2x-y)/(2(x+5y)) = (4x-3y)/(3(2x-y)) + 3(2x-y)/(6(x+5y)) = (4x-3y)/(3(2x-y)) + 3(2x-y)/(6(x+5y)) = (4x-3y)/(3(2x-y)) + (2(x-y))/(3(x+5y)) = 1 + (x-y)/(3(x+5y)).
в) x^2-9x- x(x-3)(x+3)/(x+7) = x^2-9x-x(x^2-9)/(x+7) = x^2-9x-x^3+9x/(x+7) = -x^3 + x/(x+7).
а) (7x-3y)/(2x-y) - (2y-3x)/(2x-y) = (7x-3y-2y+3x)/(2x-y) = (10x-5y)/(2x-y) = 5(2x-y)/(2x-y) = 5.
б) (4x-3y)/(6x-3y) + (2x-y)/(2x+5y) = (4x-3y)/(3(2x-y)) + (2x-y)/(2(x+5y)) = (4x-3y)/(3(2x-y)) + (2x-y)/(2(x+5y)) = (4x-3y)/(3(2x-y)) + 3(2x-y)/(6(x+5y)) = (4x-3y)/(3(2x-y)) + 3(2x-y)/(6(x+5y)) = (4x-3y)/(3(2x-y)) + (2(x-y))/(3(x+5y)) = 1 + (x-y)/(3(x+5y)).
в) x^2-9x- x(x-3)(x+3)/(x+7) = x^2-9x-x(x^2-9)/(x+7) = x^2-9x-x^3+9x/(x+7) = -x^3 + x/(x+7).