Question

Помогите решить задания от 2.1 до 2.5

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Answer 1

$\frac{sin\alpha+sin3\alpha}{cos\alpha+cos3\alpha} = \frac{2sin(2\alpha)cos(-\alpha)}{2cos(2\alpha)cos(-\alpha)} = \frac{sin2\alpha}{cos2\alpha} = tg2\alpha$

$3^{x+3} + 5*3^{x-1}= 86\\(3^4+5)*3^{x-1}=86\\(81+5)*3^{x-1}=86\\3^{x-1}=1\\3^{x-1}=3^0\\x-1=0\\x=1$