Решение №12012: \(\frac{n^{2}}{m(m+n)}-\frac{m-n}{3m}=\frac{3n^{2}-(m-n)(m+n)}{3m(m+n)}=\frac{3n^{2}-(m^{2}+mn-mn-n^{2})}{3m(m+n)}=\frac{3n^{2}-m^{2}+n^{2}}{3m(m+n)}=\frac{4n^{2}-m^{2}}{3m(m+n)}; m \neq 0, m+n \neq 0; m \neq -n\)

Ответ: \(m \neq -n\)

Решение №12015: \(\frac{y-x}{x(x-a)}-\frac{y-a}{a(x-a)}=\frac{a(y-x)-(y-a)x}{ax(x-a)}=\frac{ay-ax-yx+ax}{ax(x-a)}=\frac{ay-yx}{ax(x-a)}\frac{y(a-x)}{ax(x-a)}=\frac{-y(x-a)}{ax(x-a)}=-\frac{y}{ax}; x \neq 0, a \neq 0; x-a \neq 0, x \neq a\)

Ответ: \(x \neq a\)

Решение №12020: \(\frac{9t}{p(3t-b)}-\frac{p}{t(3t-p)}=\frac{9t^{2}-p^{2}}{pt(3t-p)}=\frac{(3t-p)(3t+p)}{pt(3t-p)}=\frac{3t+p}{pt}; p \neq 0, t \neq 0, 3t-p \neq 0, -p \neq -3t, p \neq 3t\)

Ответ: \(p \neq 3t\)

Решение №12023: \(\frac{c}{b(c-b)}+\frac{b}{c(b-c)}=\frac{}{}=\frac{}{}=\frac{}{}; x+2 \neq 0, x \neq -2; 3z \neq 0, z \neq 0\)

Ответ: \(z \neq 0\)

Решение №12024: \(\frac{6}{a(a-2)}+\frac{3}{2-a}=\frac{6}{a(a-2)}-\frac{3}{a-2}=\frac{6-3a}{a(a-2)}=\frac{3(2-a)}{a(a-2)}=-\frac{3(a-2)}{a(a-2)}=-\frac{3}{a}; a \neq 0, a-2 \neq 0; a \neq 2\)

Ответ: \(a \neq 2\)

Решение №12026: \(\frac{x}{x+y}+\frac{y}{x-y}=\frac{x(x-y)+y(x+y)}{(x+y)(x-y)}=\frac{-x^{2}-xy+xy+y^{2}}{x^{2}-y^{2}}=\frac{x^{2}+y^{2}}{x^{2}-y^{2}}\)

Ответ: \(\frac{x^{2}+y^{2}}{x^{2}-y^{2}}\)

Решение №12029: \(\frac{p+2}{p+1}-\frac{p+6}{p+3}=\frac{(p+2)(p+3)-(p+6)(p+1)}{(p+1)(p+3)}=\frac{p^{2}+3p+2p+6 \cdot (p^{2}+p+6p+6)}{(p+1)(p+3)}=\frac{p^{2}+5p+6-p^{2}-7p-6}{(p+1)(p+3)}=\frac{-2p}{(p+1)(p+3)}\)

Ответ: \(\frac{-2p}{(p+1)(p+3)}\)

Решение №12030: \(\frac{c-d}{2d(c+d)}+\frac{c+d}{2d(c-d)}=\frac{(c-d)(c-d)+(c+d)(c+d)}{2d(c+d)(c-d)}=\frac{(c-d)^{2}+(c+d)^{2}}{2d(c+d)(c-d)}=\frac{c^{2}-2cd+d^{2}+c^{2}+2cd+d^{2}}{2d(c^{2}-d^{2})}=\frac{2c^{2}+2d^{2}}{2d(c^{2}-d^{2})}=\frac{2(c^{2}+d^{2})}{2d(c^{2}-d^{2})}=\frac{c^{2}+d^{2}}{d(c^{2}-d^{2})}\)

Ответ: \(\frac{c^{2}+d^{2}}{d(c^{2}-d^{2})}\)

Решение №12031: \(\frac{x+4y}{5y(x+y)}-\frac{x-y}{5y(x-4y)}=\frac{(x+4y)(x-4y)-(x-y)(x+y)}{5y(x+y)(x-4y)}=\frac{x^{2}-16y^{2}-(x^{2}-y^{2})}{5y(x+y)(x-4y)}=\frac{x^{2}-16-x^{2}+y^{2}}{5y(x+y)(x-4y)}=\frac{-15y^{2}}{5y(x+y)(x-4y)}=\frac{-3y}{(x+y)(x-4y)}\)

Ответ: \(\frac{-3y}{(x+y)(x-4y)}\)

Решение №12033: \(\frac{d-c}{3c(2c+d)}+\frac{2c-d}{3c(c+d)}=\frac{(d-c)(c+d)+(2c-d)(2c+d)}{3c(2c+d)(c+d)}=\frac{d^{2}-c^{2}-(4c^{2}-d^{2})}{3c(2c+d)(c+d)}=\frac{d^{2}-c^{2}-4c^{2}+d^{2}}{3c(2c+d)(c+d)}=\frac{2d^{2}-5c^{2}}{3c(2c+d)(c+d)}\)

Ответ: \(\frac{2d^{2}-5c^{2}}{3c(2c+d)(c+d)}\)