Giải thích các bước giải:
a.$\dfrac{1}{3x-2}-\dfrac{1}{3x+2}=\dfrac{3x+2-(3x-2)}{(3x-2)(3x+2)}=\dfrac{4}{(3x-2)(3x+2)}$
b.$\dfrac{3xy^2}{4(x+1)}.\dfrac{(x+1)^2}{xy^3}=\dfrac{3(x+1)}{4y}$
c.$\dfrac{1}{x}-\dfrac{1}{x+1}=\dfrac{x+1-x}{x(x+1)}=\dfrac{1}{x(x+1)}$
d.$\dfrac{4x+3}{5x(x-7)}+\dfrac{48-x}{5x(x-7)}=\dfrac{4x+3+48-x}{5x(x-7)}=\dfrac{3x+51}{5x(x-7)}$
e.$\dfrac{25-x^2}{2x+6}.(-\dfrac{4x+12}{x-5})=\dfrac{(5-x)(5+x)}{2(x+3)}.\dfrac{4(x+3)}{5-x}=2(x+5)$
