Вправи: 837

837. Розв’яжіть рівняння:

1) x2+ 2x3 = 4x+15; 5(x² + 2x) = 3(4x + 1); 5x² + 10x = 12x + 3;

5x² + 10x – 12x – 3 = 0; 5x² – 2x – 3 = 0;

D = (–2)² – 4 • 5 • (–3) = 4 + 60 = 64; D = 8;

х₁ = 2+82 • 5 = 1; х₂ = 2-810 = –0,6.

2) x+23 + x2-12 = 13|х6;

2 (x + 2) + 3(x² – 1) = 2; 2x + 4 + 3x² – 3 – 2 = 0;

3x² + 2x – 1 = 0;

D = 2² – 4 • 3 • (–1) = 4 + 12 = 16; D = 4;

х₁ = -2+42 • 3 = 26 = 13; х₂ = -2-46 = –1.