Question

представьте в виде двоби срочно ​

Answer 1

1)

$\frac{15a}{b} + \frac{19a}{b} = \frac{15a + 19a}{b} = \frac{34a}{b}$

2)

$\frac{3x}{x + y} + \frac{3y}{x + y} = \frac{3x + 3y}{x + y} = \frac{3(x + y)}{x + y} = 3$

3)

$\frac{n}{m - n} - \frac{m}{m - n} = \frac{n - m}{m - n} = \frac{ - (m - n)}{m - n} = - 1$

4)

$\frac{ {a}^{2} + 4}{2 - a} - \frac{3 {a}^{2} - 4 }{2 - a} = \frac{ {a}^{2} + 4 - 3 {a}^{2} + 4}{2 - a} = \frac{8 - 2 {a}^{2} }{2 - a} = \frac{2(4 - {a}^{2} )}{2 - a} = \frac{2( {2}^{2} - {a}^{2} ) }{2 - a} = \frac{2(2 - a)(2 + a)}{2 - a} = 2(2 + a) = 4 + 2a$

5)

$\frac{ {a}^{2} - 4a}{ {a}^{2} - 9} - \frac{2a - 9}{ {a}^{2} - 9} = \frac{ {a}^{2} - 4a - 2a + 9}{ {a}^{2} - 9} = \frac{ {a}^{2} - 6a + 9}{ {a}^{2} - {3}^{2} } = \frac{ {(a - 3)}^{2} }{(a - 3)(a + 3)} = \frac{(a - 3)(a - 3)}{(a - 3)(a + 3)} = \frac{a - 3}{a + 3}$