第23页 - 启东中学作业本八年级数学人教版

$ 解:\frac {x}{ac}=\frac {xb}{abc}$

$\frac {y}{bc}=\frac {ya}{abc}$

$解:\frac{1}{4x^{3}y}=\frac {3y}{12x^{3}y^{2}}$

$\frac {4}{6xy^{2}}=\frac {8x^{2}}{12x^{3}y^{2}}$

$解:\frac{a}{2a+6}=\frac{a(a-3)}{2(a+3)(a-3)}$

$\frac{a-1}{a^{2}-9}=\frac{2a-2}{2(a+3)(a-3)}$

$解:\frac{2a}{a^{2}-9}=\frac{2a(a-3)}{(a-3)^{2}(a+3)}$

$\frac {3}{a^{2}-6a+9}=\frac {3(a+3)}{(a-3)^{2}(a+3)}$

$解:\frac{a-1}{(a+1)^{2}-4}=\frac{1}{a+3}=\frac{2(a-1)}{2(a-1)(a+3)}$

$\frac{1-a}{2-4a+2a^{2}}=-\frac{1}{2(a-1)}=-\frac{a+3}{2(a-1)(a+3)}$

$解:\frac{1}{x^{2}-x}=\frac {x-1}{x(x-1)^{2}}$

$\frac {1}{x^{2}-2x+1}=\frac {x}{x(x-1)^{2}}$

$解:\frac{2x}{x^{2}-9}=\frac{4x}{2(x+3)(x-3)}$

$\frac {x}{2x+6}=\frac{x(x-3)}{2(x+3)(x-3)}$

$解:\frac{x}{4a(x+2)}=\frac{3bx}{12ab(x+2)}$

$\frac {y}{6b(x+2)}=\frac {2ay}{12ab(x+2)}$

$解:\frac{a-1}{a^{2}+2a+1}=\frac{(a-1)^{2}}{(a+1)^{2}(a-1)}$

$\frac{6}{a^{2}-1}=\frac{6(a+1)}{(a+1)^{2}(a-1)}\ $

$解:\frac{1}{x-1}=\frac{x(x+1)}{x(x+1)(x-1)}$

$\frac {1}{x^{2}-1}=\frac {x}{x(x+1)(x-1)}$

$\frac {1}{x^{2}+x}=\frac {x-1}{x(x+1)(x-1)}$