Question

Решите уравнение: 1) (7 - 2x) (49 + 14х + 4х²) + 2x(2x – 5) (2x + 5) = 43
2) 100(0,2х + 1) (0, 04x²–0,2х+1) = 5x(0,16х²– 4)

Answer 1

$1)(7-2x)(49+14x+4x ^ { 2 } )+2x(2x-5)(2x+5)=43 \\ 343-8x^{3}+2x \times (4x {}^{2} - 25) = 43 \\ 343-8x^{3}+8x^{3}-50x=43 \\ 343-50x=43 \\ -50x=43-343 \\ -50x=-300 \\ x=\frac{-300}{-50} \\ x = 6$

$2)100(0.2x+1)(0.04x ^ { 2 } -0.2x+1)=5x(0.16x ^ { 2 } -4) \\ \left(20x+100\right)\left(0.04x^{2}-0.2x+1\right)=5x\left(0.16x^{2}-4\right) \\ 0.8x^{3}+100=5x\left(0.16x^{2}-4\right) \\ 0.8x^{3}+100=0.8x^{3}-20x \\ 0.8x^{3}+100-0.8x^{3}=-20x \\ 100=-20x \\ -20x=100 \\ x=\frac{100}{-20} \\ x = - 5$