39x+6=21x^2

Solution for 39x+6=21x^2 equation:

39x+6=21x^2

We move all terms to the left:

39x+6-(21x^2)=0

determiningTheFunctionDomain
-21x^2+39x+6=0

a = -21; b = 39; c = +6;
Δ = b2-4ac
Δ = 392-4·(-21)·6
Δ = 2025
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2025}=45$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(39)-45}{2*-21}=\frac{-84}{-42}
=+2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(39)+45}{2*-21}=\frac{6}{-42}
=-1/7
$