Question

${x}^{2} + 4 {x}^{2} - 4x - 16 = 0$
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Answer 1

${x}^{2} + 4 {x}^{2} - 4x - 16 = 0$

$5x^2-4x-16=0$

$D_1=(-2)^2-5\cdot(-16)=4+80=84$

$x=\dfrac{2\pm\sqrt{84}}{5} =\dfrac{2\pm2\sqrt{21}}{5}$

Ответ: $\dfrac{2\pm2\sqrt{21}}{5}$