Ответ(ы) на вопрос:
Гость
1)
[latex]log_ \frac{1}{3} (x-1) \geq -2 \\ \left \{ {{x-1 \leq 9} \atop {x-1\ \textgreater \ 0}} \right. \\ \left \{ {{x\leq10} \atop {x\ \textgreater \ 1}} \right. [/latex]
x ∈ (1; 10]
2)
[latex]13^{2x+1} -13^x-12=0 \\ 13^x=t \\ 13t^2-t-12=0 \\ D=1+13*48=625 \\ x_1=- \frac{12}{13} \\ x_2=1 \\ \\ 13^x=- \frac{12}{13} \\ 13^x=1[/latex]
x ∈ ∅
x = 0
x = 0
3) cos α = 0,8; 0 < α < π/2
[latex] \left \{ {{|sin \alpha|= \sqrt{1-0,8^2} } \atop {0\ \textless \ \alpha \ \textless \ \frac{ \pi }{2} }} \right. [/latex]
sin α = 0,6
tg α = sin α / cos α = 0,6/0,8 = 3/4
ctg α = 1 / tg α = 4/3
4)
[latex] \sqrt{x-1}=x-3 \\ \left \{ {{x-1=x^2-6x+9} \atop {x-3 \geq 0}} \right.\\ \left \{ {{x^2-7x+10=0} \atop {x \geq 3}} \right.\\ \left \{ {{x_1=2;x_2=5} \atop {x \geq 3}} \right. \\ x=5 [/latex]
5)
[latex] \sqrt{2+x-x^2} \ \textgreater \ -1[/latex]
2 + x - x² ≥ 0
x² - x - 2 ≤ 0
x² - x - 2 = 0
По теореме Виета:
x₁ = -1, x₂ = 2
x ∈ [-1; 2]
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