6x^2+21x=21

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

6x^2+21x=21

We move all terms to the left:

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

a = 6; b = 21; c = -21;
Δ = b2-4ac
Δ = 212-4·6·(-21)
Δ = 945
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:

$\sqrt{\Delta}=\sqrt{945}=\sqrt{9*105}=\sqrt{9}*\sqrt{105}=3\sqrt{105}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(21)-3\sqrt{105}}{2*6}=\frac{-21-3\sqrt{105}}{12}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(21)+3\sqrt{105}}{2*6}=\frac{-21+3\sqrt{105}}{12}
$