1) 4/13*√4*1/3*√9*3/4=4/13*√13/3*√39/4=4*√13*√39/13*√3*2=2√507/13√3=2√169/13=2*13*13=2
5) 6/11*√1*2/9*√11=6/11*√11/9*√11=6*√11*√11/11*3=2*11/11=2
8) 9d^2/7cd^2-6cd=9d^2/cd(7d-6)=9d/7cd-6c
11) 54v^2/18uv^2+12uv=54v^2/6uv(3v+2)=9v/3vu+2u
13) 2/3√2*1/4=2/3*³9/4=2/3*3/2=1
14) -x^2-225=0
-x^2=225
x^2=-225
x1=-15
x2=15
5х-2х= - 4-5
3х=-9
х=-9:3
<span>х=-3</span>
<em>Приводим к общему знаменателю.</em>
![\frac{1}{a} -\frac{a^2-25}{5a}+\frac{a}{5}=\frac{5-a^2+25+a^2}{5a}=\frac{30}{5a}=\frac{6}{a}](https://tex.z-dn.net/?f=%5Cfrac%7B1%7D%7Ba%7D+-%5Cfrac%7Ba%5E2-25%7D%7B5a%7D%2B%5Cfrac%7Ba%7D%7B5%7D%3D%5Cfrac%7B5-a%5E2%2B25%2Ba%5E2%7D%7B5a%7D%3D%5Cfrac%7B30%7D%7B5a%7D%3D%5Cfrac%7B6%7D%7Ba%7D)
если
, то ![\frac{6}{a}=6\cdot3=18](https://tex.z-dn.net/?f=%5Cfrac%7B6%7D%7Ba%7D%3D6%5Ccdot3%3D18)
Ответ: ![18](https://tex.z-dn.net/?f=18)