-7x-21x^2=0

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Solution for -7x-21x^2=0 equation:



-7x-21x^2=0
a = -21; b = -7; c = 0;
Δ = b2-4ac
Δ = -72-4·(-21)·0
Δ = 49
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{49}=7$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-7)-7}{2*-21}=\frac{0}{-42} =0 $
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-7)+7}{2*-21}=\frac{14}{-42} =-1/3 $

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