21x^2-40x=0

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Solution for 21x^2-40x=0 equation: 



21x^2-40x=0

a = 21; b = -40; c = 0;
Δ = b2-4ac
Δ = -402-4·21·0
Δ = 1600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1600}=40$


$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-40)-40}{2*21}=\frac{0}{42}
=0
$


$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-40)+40}{2*21}=\frac{80}{42}
=1+19/21
$

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