a) M = ( $\frac{√x-2}{x-1}$ - $\frac{√x+2}{x+2√x+1}$ ) . $\frac{x²-2x+1}{2}$ ( x ≥0 , x $\neq$ 1 )
= [ $\frac{(√x-2)(√x+1)}{(√x+1)²(√x-1)}$ - $\frac{(√x+2)(√x-1)}{(√x+1)²(√x-1)}$ ] . $\frac{(x-1)²}{2}$
= [ $\frac{x+√x-2√x-2-x+√x-2√x+2}{(x-1)²(√x+1)}$ ] . $\frac{(x-1)²}{2}$
= [ $\frac{-2√x}{(x-1)²(√x+1)}$ ] . $\frac{(x-1)²}{2}$
= $\frac{-√x}{√x+1}$
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