5x^4=81
5x^4=3^4
5x=3
x=3/5=0.6
проверка:
(5*0,6)^4=81
3^4=81
81=81
(x² - 16)(x² + 2x - 8)(x - 2) ≥ 0
(x - 4)(x + 4)(x² + 2x + 1 - 9)(x - 2) ≥ 0
(x - 4)(x + 4)[(x + 1)² - 3²](x - 2) ≥ 0
(x - 4)(x + 4)(x + 1 - 3)(x + 1 + 3)(x - 2) ≥ 0
(x - 4)(x + 4)(x - 2)(x + 4)(x - 2) ≥ 0
(x - 4)(x + 4)²(x - 2)² ≥ 0
Нули: x = -4; 2; 4.
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---------------●------------------------------●-----------------<span>●</span>---------------------> x
- -4 - 2 - 4 +
Ответ: x ∈ {-4} U {2} U [4; +∞).
1) <span>Решение : </span>
<span>7x + 9 = 100 </span>
<span>7x = 100 -9 </span>
<span>x = 91: 7 </span>
<span>x = 13 </span>