=7²/7^3 +9*2/21 =1/7 +3*2/7 =1/7 +6/7 =(1 +6) /7 =7/7 =1
0.5*6561+1,1*(-729)-28=3280,5-801,9-28=2450,6
Думаю тут лишнее -2 переписали не верно;
делим на ![25^x](https://tex.z-dn.net/?f=25%5Ex)
![5*\frac{4^x}{25^x}+3*-\frac{2^x*5^x}{5^x5^x}=2](https://tex.z-dn.net/?f=5%2A%5Cfrac%7B4%5Ex%7D%7B25%5Ex%7D%2B3%2A-%5Cfrac%7B2%5Ex%2A5%5Ex%7D%7B5%5Ex5%5Ex%7D%3D2)
![5((\frac{2}{5})^x)^2+3(\frac{2}{5})^x-2=0](https://tex.z-dn.net/?f=5%28%28%5Cfrac%7B2%7D%7B5%7D%29%5Ex%29%5E2%2B3%28%5Cfrac%7B2%7D%7B5%7D%29%5Ex-2%3D0)
замена
t>0;
5t²+3t-2=0;
D=9+4*2*5=49;
t=(-3+7)/10=2/5;
t=(-3-7)/10=-1; ∅;
![(\frac{2}{5})^x=(\frac{2}{5})^1](https://tex.z-dn.net/?f=%28%5Cfrac%7B2%7D%7B5%7D%29%5Ex%3D%28%5Cfrac%7B2%7D%7B5%7D%29%5E1)
x=1;
Π=180 градусов
a) sin13π/6=sin390=sin(360+30)=sin30=
![\frac{1}{2}](https://tex.z-dn.net/?f=+%5Cfrac%7B1%7D%7B2%7D+)
б) tg(-11π/6)=-tg330=-tg(360-30)=-tg30=-
![\frac{ \sqrt{3} }{3}](https://tex.z-dn.net/?f=+%5Cfrac%7B+%5Csqrt%7B3%7D+%7D%7B3%7D+)
в) cosπ+ctg4π/6=cos180+ctg120=-1+ctg(180-60)=-1+(-ctg60)=-1-ctg60=-1-
![\frac{ \sqrt{3} }{3}](https://tex.z-dn.net/?f=+%5Cfrac%7B+%5Csqrt%7B3%7D+%7D%7B3%7D+)