Відповіді на вправи: 468

1) x² – 25 $\le$ 0;

x² – 25 = 0;

x² = 25;

x₁ = –5, x₂ = 5.

x $\in$ [–5; 5].

2) –x² $\ge$ 81;

–x² – 81 $\ge$ 0;

–x² – 81 = 0;

–x² = 81;

D < 0.

$\varnothing$.

3) 3x² – 6x > 0;

3x² – 6x = 0;

х(3х – 6) = 0;

x = 0, 3х – 6 = 0;

3х = 6, x = 2.

x $\in$ (–$\infty$; 0) $\cup$ (2; +$\infty$).

4) 3x² – 6x $\ge$ 0;

3x² – 6x = 0

x(3x – 6) = 0

x = 0, 3x – 6 = 0;

3x = 6, x = 2.

x $\in$ (–$\infty$; 0] $\cup$ [2; +$\infty$).

5) x² + 4 < 0;

x² + 4 = 0;

x² = –4;

D < 0.

$\varnothing$.

6) –2x² – 4x $\ge$ 0;

–2x² – 4x = 0;

–2x(x + 2) = 0;

x₁ = 0, x₂ = –2.

x $\in$ (–$\infty$; –2] $\cup$ [0; +$\infty$).