9d^2-7d-1=0

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Solution for 9d^2-7d-1=0 equation: 



9d^2-7d-1=0

a = 9; b = -7; c = -1;
Δ = b2-4ac
Δ = -72-4·9·(-1)
Δ = 85
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-7)-\sqrt{85}}{2*9}=\frac{7-\sqrt{85}}{18}
$


$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-7)+\sqrt{85}}{2*9}=\frac{7+\sqrt{85}}{18}
$

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