21w2-4w-1=0

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Solution for 21w2-4w-1=0 equation:



21w^2-4w-1=0
a = 21; b = -4; c = -1;
Δ = b2-4ac
Δ = -42-4·21·(-1)
Δ = 100
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$w_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$w_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{100}=10$
$w_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-4)-10}{2*21}=\frac{-6}{42} =-1/7 $
$w_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4)+10}{2*21}=\frac{14}{42} =1/3 $

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