Преобразуем 1-е уравнение
log(осн3)от х - log(осн3) от у = 1
log (осн3) от х/у = log (осн3) от 3
х/у = 3 → х = 3у
подставим во 2-е уравнение
3у - 2у = 21 → у = 21
х = 3· 21 = 63
Ответ: х = 63; у = 21
1 - Д
2 - Д
4- С..........................
1) (b⁻⁴)⁸ : b¹⁶= b⁻³² : b¹⁶ = b⁻³²⁻¹⁶ = b⁻⁴⁸
![2)(-\frac{4a^{6} }{b^{3} })^{2}=\frac{4^{2}*(a^{6})^{2}}{(b^{3})^{2}}=\frac{16a^{12} }{b^{6}}\\\\3)(\frac{2m^{2}n^{3}}{3k^{6}})^{4}=\frac{2^{4}*(m^{2})^{4}*(n^{3})^{4}}{3^{4}*(k^{6})^{4} }=\frac{16m^{8}n^{12}}{81k^{24} }](https://tex.z-dn.net/?f=2%29%28-%5Cfrac%7B4a%5E%7B6%7D+%7D%7Bb%5E%7B3%7D+%7D%29%5E%7B2%7D%3D%5Cfrac%7B4%5E%7B2%7D%2A%28a%5E%7B6%7D%29%5E%7B2%7D%7D%7B%28b%5E%7B3%7D%29%5E%7B2%7D%7D%3D%5Cfrac%7B16a%5E%7B12%7D+%7D%7Bb%5E%7B6%7D%7D%5C%5C%5C%5C3%29%28%5Cfrac%7B2m%5E%7B2%7Dn%5E%7B3%7D%7D%7B3k%5E%7B6%7D%7D%29%5E%7B4%7D%3D%5Cfrac%7B2%5E%7B4%7D%2A%28m%5E%7B2%7D%29%5E%7B4%7D%2A%28n%5E%7B3%7D%29%5E%7B4%7D%7D%7B3%5E%7B4%7D%2A%28k%5E%7B6%7D%29%5E%7B4%7D+%C2%A0+%7D%3D%5Cfrac%7B16m%5E%7B8%7Dn%5E%7B12%7D%7D%7B81k%5E%7B24%7D+%7D)
4)
![1)\frac{a+1}{a-1}-\frac{4a}{a^{2}-1 } =\frac{a+1}{a-1}-\frac{4a}{(a-1)(a+1)}=\frac{a^{2}+2a+1-4a }{(a-1)(a+1)}=\frac{a^{2}-2a+1 }{(a-1)(a+1)}=\frac{(a-1)^{2} }{(a-1)(a+1)}=\frac{a-1}{a+1}\\\\2)\frac{a-1}{a+1}:\frac{a-1}{a^{2}+a }=\frac{a-1}{a+1}*\frac{a(a+1)}{a-1}=a](https://tex.z-dn.net/?f=1%29%5Cfrac%7Ba%2B1%7D%7Ba-1%7D-%5Cfrac%7B4a%7D%7Ba%5E%7B2%7D-1+%7D+%3D%5Cfrac%7Ba%2B1%7D%7Ba-1%7D-%5Cfrac%7B4a%7D%7B%28a-1%29%28a%2B1%29%7D%3D%5Cfrac%7Ba%5E%7B2%7D%2B2a%2B1-4a+%7D%7B%28a-1%29%28a%2B1%29%7D%3D%5Cfrac%7Ba%5E%7B2%7D-2a%2B1+%7D%7B%28a-1%29%28a%2B1%29%7D%3D%5Cfrac%7B%28a-1%29%5E%7B2%7D+%7D%7B%28a-1%29%28a%2B1%29%7D%3D%5Cfrac%7Ba-1%7D%7Ba%2B1%7D%5C%5C%5C%5C2%29%5Cfrac%7Ba-1%7D%7Ba%2B1%7D%3A%5Cfrac%7Ba-1%7D%7Ba%5E%7B2%7D%2Ba+%7D%3D%5Cfrac%7Ba-1%7D%7Ba%2B1%7D%2A%5Cfrac%7Ba%28a%2B1%29%7D%7Ba-1%7D%3Da)
<span>5a(a-b+c)+3b(a-b-c)-4c(a+b-c)=5a²-5ab+5ac+3ab-3b²-3bc-4ac-4bc+4c²=
=5a²-3b²+4c²-2ab+ac-7bc</span>