<span>2^x - 8*2^(-x) = 7 умножим на 2^x
2^(2x) - 7*2^(x) - 8 = 0
2^(x) = t, t > 0
t</span>² - 7t - 8 = 0
t₁ = -1 не удовлетворяет условию t > 0
t₂ = 8
2^(x) = 8
2^(x) = 2³
x = 3
Ответ: х = 3
Tg²a-sin²a(1+tg²a) = tg²a-sin²a(1/cos²a) = tg²a-tg²a = 0
x² = 30 - x
x² + x - 30 = 0
a = 1; b = 1; c = - 30
D = b² - 4ac = 1² - 4 * 1 * (-30) = 1 + 120 = 121
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x1 = (-1+11)/2
x1 = 10/2
x1 = 5
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x2 = (-1-11)/2
x2 = -12/2
x2 = -6
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Ответ: x1 = 5, x2 = -6.
<span>x3-5x2-4x+20=0</span>