Решите: 1) x^4<=625 2)x^3>=216

Question

Решите:
1) x^4<=625<br> 2)x^3>=216

Answer 1

X⁴-625≤0
(x²-25)(x²+25)≤0
x²+25≥0 при x∈(-∞;+∞) =>
x²-25≤0
(x-5)(x+5)≤0
x∈[-5;5]

x³≥216
x³-216≥0
(x-6)(x²+6x+36)≥0
x²+6x+36=0
D=6²-4*36<0 => x²+6x+36>0 при x∈(-∞;+∞) =>
x-6≥0
x≥6