Question

5х²+4х-7=0 помогите
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Answer 1

Ответ:

$x_{1,2}=\dfrac{-2 \pm \sqrt{39}}{5}$

Объяснение:

$5x^2+4x-7=0\\\\==================\\\\D = b^2-4ac\\\\a=5; \quad b=4; \quad c=-7;\\\\D=4^2-4\times5\times(-7)\\\\D=16+140\\\\D=156\\\\==================\\\\x_{1,2}=\dfrac{-b \pm \sqrt{D}}{2a}\\\\\\x_{1,2}=\dfrac{-4 \pm \sqrt{156}}{2\times 5}\\\\\\x_{1,2}=\dfrac{-4 \pm 2\sqrt{39}}{10}\\\\\\x_{1,2}=\dfrac{2(-2 \pm \sqrt{39})}{10}\\\\\\x_{1,2}=\dfrac{-2 \pm \sqrt{39}}{5}$