Question

Solo el a y el c
El b y el d no​

Answer 1

Respuesta:

Explicación paso a paso:

Answer 2

Respuesta:

 $a)~~1\\\\c)~~2$

Explicación paso a paso:

a)

   $\cfrac{2a}{a-3b}-\cfrac{3b}{a+3b}-\cfrac{~a^2+3ab+18b^2}{a^2-9b^2}\\\\\\\cfrac{~2a(a+3b)-3b(a-3b)}{(a-3b)(a+3b)}-\cfrac{~a^2+3ab+18b^2}{a^2-9b^2}\\\\\\\cfrac{2a^2+6ab-3ab+9b^2}{a^2-9b^2}-\cfrac{a^2+3ab+18b^2}{a^2-9b^2}\\\\\\\cfrac{2a^2+3ab+9b^2}{a^2-9b^2}-\cfrac{a^2+3ab+18b^2}{a^2-9b^2}$

   $\cfrac{2a^2+3ab+9b^2-(a^2+3ab+18b^2)}{a^2-9b^2}\\\\\\\cfrac{2a^2+3ab+9b^2-a^2-3ab-18b^2}{a^2-9b^2}\\\\\\\cfrac{~a^2-9b^2~}{a^2-9b^2}=1$

c)

    $(\cfrac{~x+y~}{x-y}-\cfrac{~x-y~}{x+y})\cdot\cfrac{~x^2-y^2~}{2xy}\\\\\\\cfrac{(x+y)(x+y)-(x-y)(x-y)}{(x-y)(x+y)}\cdot\cfrac{x^2-y^2}{2xy}\\\\\\\cfrac{~x^2+2xy+y^2-(x^2-2xy+y^2)~}{x^2-y^2}\cdot\cfrac{x^2-y^2}{2xy}$

   $\cfrac{~x^2+2xy+y^2-x^2+2xy-y^2~}{x^2-y^2}\cdot\cfrac{x^2-y^2}{2xy}\\\\\\\cfrac{~4xy~}{x^2-y^2}\cdot\cfrac{x^2-y^2}{2xy}\\\\\\\cfrac{~4xy~}{2xy}=\cfrac{~4~}{2}=2$