<span> (х-3у)/у = 6
x/y-3=6
x/y=9</span>
ОДЗ:
а) x² -6≥0
(x-√6)(x+√6)≥0
x=√6 x= -√6
+ - +
------- -√6 ------------ √6 ------------
\\\\\\\\\\ \\\\\\\\\\\\\\\
x∈(-∞; -√6]U[√6; +∞)
b) 3-x≥0
-x≥ -3
x≤3
В итоге ОДЗ: х∈(-∞; -√6]U[√6; 3]
x²-6=(3-x)²
x²-6=9-6x+x²
x²-x²+6x=9+6
6x=15
x=15 : 6
x=2.5
Ответ: 2,5
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(х+9)(х^2-9х+81)= -7-4x+x^3
х³+9х²-9х²-81х+81х+729 = -7 - 4х + х³
4х + 729 = -7
х = (-7-729)/4 = -736/4 = -184
Sin(π/2+a)=cosa
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