Đáp án:
`a,`
A= $\frac{5x^2-10xy}{2(2y-x)^3}$
= $\frac{5x.x-5x.2y}{-2(x - 2y)^3}$
= $\frac{5x(x - 2y)}{-2(x - 2y)^3}$
= $\frac{5x}{-2(x - 2y)^2}$
`b,`
B= $\frac{16-(x + 1)^2}{x^2+10x+25}$
= $\frac{4^2-(x+1)^2}{x^2+2.x.5+5^2}$
= $\frac{[4 -(x +1)].[4+x+1]}{(x+5)^2}$
= $\frac{(3-x)(x+5)}{(x+5)^2}$
= $\frac{3 -x}{x + 5}$
`c,`
C= $\frac{x^2 + 5x + 6}{x^2 - 4}$
= $\frac{x^2 + 2x + 3x + 6}{x^2 - 2^2}$
= $\frac{x(x + 2) + 3(x + 2)}{(x - 2)(x + 2)}$
= $\frac{(x + 3)(x + 2)}{(x -2)(x+2)}$
= $\frac{x + 3}{x - 2}$
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