Question

4+8x-5x²=0 умоляю помогитеее
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Answer 1

Решение и ответ:

4 + 8x - 5x² = 0

$D={b^2}-4ac={8^2}-4 \cdot (-5) \cdot 4=64+80=144$

$\displaystyle {x_{1;2}}=\frac{{-b\pm\sqrt D}}{{2a}}=\frac{{-8\pm\sqrt{144}}}{{2 \cdot (-5)}}= \frac{{ -8\pm12}}{{-10}}$

$\displaystyle {x_1}=\frac{{-8+12}}{{-10}}=\frac{4}{{-10}}=-\frac{2}{5}=-0.4$

$\displaystyle {x_2}=\frac{{-8-12}}{{-10}}=\frac{{-20}}{{-10}}=2$

Ответ: x₁ = -0.4; x₂ = 2.