Question

11. Корнем какого из уравнений будет число 5? ​

Answer 1

Ответ: никакого

$4x + \frac{1}{4} = \frac{21}{4} \\ 4x = \frac{21}{4} - \frac{1}{4} \\ 4x = \frac{20}{4} \\ x = \frac{20}{4} \div 4 \\ x = \frac{5}{4} \\ x = 1 \frac{1}{4} \\ x = 1.25$

$2(5x - 4) = 8x + 2.4 \\ 10x - 8 = 8x + 2.4 \\ 10x - 8x = 2.4 + 8 \\ 2x = 10.4 \\ x = 10.4 \div 2 \\ x = 5.2$

$( \frac{x}{5} - 2) + (x + 2) = 15 \\ 0.2x - 2 + x + 2 = 15 \\ 1.2x = 15 \\ x = \frac{15}{1.2} \\ x = \frac{150}{12} \\ x = \frac{25}{2} \\ x = 12.5$

$3x - 4.5 = 15 \\ 3x = 15 + 4.5 \\ 3x = 19.5 \\ x = 19.5 \div 3 \\ x = 6.5$