Question

5x2(в квадрате) +2x-7=0

Answer 1

Решение и ответ:

$\displaystyle 5{x^2}+2x-7=0\\D={b^2}-4ac={2^2}-4 \cdot 5 \cdot (-7)=4+140=144\\\\{x_{1;2}}=\frac{{-b \pm \sqrt D}}{{2a}}=\frac{{-2 \pm \sqrt {144} }}{{2 \cdot 5}} = \frac{{ - 2 \pm 12}}{{10}}\\\\{x_1}=\frac{{-2+12}}{{10}} = \frac{{10}}{{10}}=1\\\\{x_2}=\frac{{-2-12}}{{10}} = \frac{{-14}}{{10}} =-1,4$

Ответ: x₁ = 1; x₂ = -1,4