Giải thích các bước giải:
$a,$ $\frac{1-3x}{2}$ $-$ $\frac{x+3}{2}$
$=$ $\frac{1-3x - (x+3)}{2}$
$=$ $\frac{1-3x-x-3}{2}$
$=$ $\frac{-4x- 2}{2}$
$=$ $\frac{2(-2x-1)}{2}$
$=$ $-2x-1$
$b,$ $\frac{2(x+y)(x-y)}{x}$ $-$ $\frac{-2y²}{x}$ $ĐK : x≠ 0$
$=$ $\frac{2(x²-y²)}{x}$ + $\frac{2y²}{x}$
$=$ $\frac{2(x² -y²) + y²}{x}$
$=$ $\frac{2x² - 2y² + 2y²}{x}$
$=$ $\frac{2x²}{x}$
$= 2x$
$c,$ $\frac{3x+1}{x+y}$ $-$ $\frac{2x-3}{x+y}$ $ĐK : x ≠ - y$
$=$ $\frac{3x+1-(2x-3)}{x+y}$
$=$ $\frac{3x + 1-2x + 3}{x+y}$
$=$ $\frac{x +4}{x + y}$
$d,$ $\frac{xy}{2x - y}$ $-$ $\frac{x² - 1 }{y - 2x}$ $ĐK : y ≠ 2x$
$=$ $\frac{-xy}{y-2x}$ - $\frac{x²-1}{y-2x}$
$=$ $\frac{-xy-(x²-1)}{y-2x}$
$=$ $\frac{-x² - xy + 1}{y-2x}$
$e,$ $\frac{4x - 1}{3x²y}$ - $\frac{7x - 1}{3x²y}$ $ĐK : x≠0 , y≠0$
$=$ $\frac{4x - 1 - (7x - 1)}{3x²y}$
$=$ $\frac{4x - 1-7x+1}{3x²y}$
$=$ $\frac{-3x}{3x²y}$
$=$ $\frac{-1}{xy}$
