Краткий ответ
\(-1\); 2) \(-2\); 3) \(\frac15\); 4) \(-2\); 5) \(-\frac1{12}\); 6) \(\frac{a+5}{5-a}\); 7) \(\frac1b\); 8) \(1\).
\(-\frac23\); 10) \(-\frac5a\); 11) \(-\frac x2\); 12) \(\frac53\); 13) \(\frac13\); 14) \(a\); 15) \(\frac{1-y}{1+y}\); 16) \(1-y\).
\(-\frac2{a-b}\); 18) \(\frac1{x-3}\); 19) \(\frac{1-b}{1+b}\); 20) \(\frac{a+3}{a-3}\); 21) \(\frac{y-2}{y+2}\); 22) \(\frac1{a+2}\); 23) \(1\); 24) \(1\).
Ключевые шаги
Используем: \[ u-v=-(v-u), \qquad 3-x=-(x-3), \] а одинаковые множители сокращаем только при условии, что они не равны нулю.
\(\displaystyle -\frac{x+y}{x+y}=-1,\quad x+y\ne0.\)
\(\displaystyle \frac{-2(a+b)}{a+b}=-2,\quad a+b\ne0.\)
\(\displaystyle \frac{-(x+3)}{-5(x+3)}=\frac15,\quad x\ne-3.\)
\(\displaystyle \frac{2(b+1)}{-(b+1)}=-2,\quad b\ne-1.\)
\(\displaystyle \frac{-(x-3)}{12(x-3)}=-\frac1{12},\quad x\ne3.\)
\[ \frac{(a+5)^2}{(a+5)(5-a)} =\frac{a+5}{5-a}, \quad a\ne-5,\ a\ne5. \]
\[ \frac{x+13}{(x+13)b}=\frac1b, \quad x\ne-13,\ b\ne0. \]
\[ \frac{-(y-1)}{-(-1+y)}=1, \quad y\ne1. \]
\[ \frac{2(a-b)}{3(b-a)} =\frac{2(a-b)}{-3(a-b)} =-\frac23, \quad a\ne b. \]
\[ \frac{5(x-y)}{a(y-x)} =\frac{5(x-y)}{-a(x-y)} =-\frac5a, \quad a\ne0,\ x\ne y. \]
\[ \frac{x(y+3)}{2(-y-3)} =\frac{x(y+3)}{-2(y+3)} =-\frac x2, \quad y\ne-3. \]
\[ \frac{5(-2+a)}{3(a-2)} =\frac{5(a-2)}{3(a-2)} =\frac53, \quad a\ne2. \]
\[ \frac{y-1}{3(-1+y)}=\frac13, \quad y\ne1. \]
\[ \frac{a(a-1)}{-(1-a)} =\frac{a(a-1)}{a-1} =a, \quad a\ne1. \]
\[ \frac{(y-1)^2}{(1-y)(1+y)} =\frac{(y-1)^2}{-(y-1)(y+1)} =\frac{1-y}{1+y}, \quad y\ne1,\ y\ne-1. \]
\[ \frac{(y+1)(y-1)}{-y-1} =\frac{(y+1)(y-1)}{-(y+1)} =1-y, \quad y\ne-1. \]
\[ \frac{-2(a-b)}{(a-b)^2} =-\frac2{a-b}, \quad a\ne b. \]
\[ \frac{x-3}{(3-x)^2} =\frac{x-3}{(x-3)^2} =\frac1{x-3}, \quad x\ne3. \]
\[ \frac{(b-1)^2}{(1-b)(1+b)} =\frac{(b-1)^2}{-(b-1)(b+1)} =\frac{1-b}{1+b}, \quad b\ne1,\ b\ne-1. \]
\[ \frac{(a+3)(a-3)}{(3-a)^2} =\frac{(a+3)(a-3)}{(a-3)^2} =\frac{a+3}{a-3}, \quad a\ne3. \]
\[ \frac{(y-2)(y+2)}{(2+y)^2} =\frac{(y-2)(y+2)}{(y+2)^2} =\frac{y-2}{y+2}, \quad y\ne-2. \]
\[ \frac{-(a-2)}{(2-a)(a+2)} =\frac{-(a-2)}{-(a-2)(a+2)} =\frac1{a+2}, \quad a\ne2,\ a\ne-2. \]
\[ \frac{(x-1)(x+1)}{(1-x)(-x-1)} =\frac{(x-1)(x+1)}{(x-1)(x+1)} =1, \quad x\ne1,\ x\ne-1. \]
\[ \frac{-(x-1)(1-x)}{(x-1)^2} =\frac{(x-1)^2}{(x-1)^2} =1, \quad x\ne1. \]
Ограничения нужны потому, что сокращаемые множители не могут быть равны нулю в исходной дроби.
