8x2+31x+21=0

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Solution for 8x2+31x+21=0 equation:



8x^2+31x+21=0
a = 8; b = 31; c = +21;
Δ = b2-4ac
Δ = 312-4·8·21
Δ = 289
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{289}=17$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(31)-17}{2*8}=\frac{-48}{16} =-3 $
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(31)+17}{2*8}=\frac{-14}{16} =-7/8 $

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