Toán Lớp 8: A) 13z/63x²y³ ; -y/15xz² ; 2x/9y²z
B) x/x-y ; x/(x-y)² ; 1/(y-x)³
C) 1/2x+4 ; x/2x-4 ; 3/4-x²
D) 1/x-2x² ; 20/4x³-x ; 7/2x²+x
E) x/x³+1 ; x+1/x²+x ; x+2/x²-x+1
F) 1/x²+3x+2 ; 1/(x+1)² ; 1/(x+2)²
Cảm ơn mọi người nhiều ạ