Question

Решите уравнение 1) 4x(3х + 1) — 3x(4х – 1)=14;
2) 5x(2x – 7) - 2х(5х – 16)=21;
3) x(8х - 5) - 2х(4x+3)=13;
4) 2x(2x+9) - x(4х + 5) = 39.​

Answer 1

1)

$4x(3x + 1) - 3x(4x - 1) = 14 \\ 12x {}^{2} + 4x - 12x {}^{2} + 3x = 14 \\ 7x = 14 \\ x = 2$

ответ: 2

2)

$5x(2x - 7) - 2x(5x - 16) = 21 \\ 10x {}^{2} - 35x - 10x {}^{2} + 32x = 21 \\ - 3x = 21 \\ x = - 7$

ответ: - 7

3)

$x(8x - 5) - 2x(4x + 3) = 13 \\ 8x {}^{2} - 5x - 8x {}^{2} - 6x = 13 \\ - 11x = 13 \\ x = - 1 \frac{2}{11}$

ответ в формуле

4)

$2x(2x + 9) - x(4x + 5) = 39 \\ 4x {}^{2} + 18x - 4x {}^{2} - 5x = 39 \\ 13x = 39 \\ x = 3$

ответ: 3