Bt1: Thực hiện phép tính:
a/\(\left(\dfrac{2xy}{x^2-y^2}+\dfrac{x-y}{2x+2y}\right):\dfrac{x+y}{2x}+\dfrac{y}{y-x}\)
b/\(\left(\dfrac{x+2}{x+1}-\dfrac{2x}{x-1}\right)\)\(.\dfrac{3x+3}{x}+\dfrac{4x^2+x+7}{x^2-x}\)
c/\(\dfrac{1}{x^2+9x+20}+\dfrac{1}{x^2+11x+30}+\dfrac{1}{x^2+13x+42}\)
HELP ME!!!!!!!!! THỨ HAI MÌNH PHẢI KIỂM TRA RỒI