3x*(x+4)=31

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Solution for 3x*(x+4)=31 equation:



3x(x+4)=31
We move all terms to the left:
3x(x+4)-(31)=0
We multiply parentheses
3x^2+12x-31=0
a = 3; b = 12; c = -31;
Δ = b2-4ac
Δ = 122-4·3·(-31)
Δ = 516
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:
$\sqrt{\Delta}=\sqrt{516}=\sqrt{4*129}=\sqrt{4}*\sqrt{129}=2\sqrt{129}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(12)-2\sqrt{129}}{2*3}=\frac{-12-2\sqrt{129}}{6} $
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(12)+2\sqrt{129}}{2*3}=\frac{-12+2\sqrt{129}}{6} $

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