Ответ:
Как-то так, вроде. Если нужно - поменяй оформление
(6m+mn)(-12-2n) = m (6+n) - 2 (6+n) = (6+n)(m-2)
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(х^5)^2 * х^4 / х^13=x
(-1*1/3*a*b^4*c^2)^3=-(1/27) a^3 b^12 c^6
-(-3b^3)^2 * 3b^3= -27 b^9
![\frac{(n+1)!}{n!} = \frac{(n+1)*n!}{n!} =n+1 ](https://tex.z-dn.net/?f=+%5Cfrac%7B%28n%2B1%29%21%7D%7Bn%21%7D+%3D+%5Cfrac%7B%28n%2B1%29%2An%21%7D%7Bn%21%7D+%3Dn%2B1%0A%0A%0A%0A%0A%0A%0A+)
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![\frac{(n+1)!(n+3)}{(n+4)!}=\frac{1}{(n+2)(n+4)}](https://tex.z-dn.net/?f=++%5Cfrac%7B%28n%2B1%29%21%28n%2B3%29%7D%7B%28n%2B4%29%21%7D%3D%5Cfrac%7B1%7D%7B%28n%2B2%29%28n%2B4%29%7D+)