(x+3)(21)(x)=2730

Solution for (x+3)(21)(x)=2730 equation:

(x+3)(21)(x)=2730

We move all terms to the left:

(x+3)(21)(x)-(2730)=0

We multiply parentheses

21x^2+63x-2730=0

a = 21; b = 63; c = -2730;
Δ = b2-4ac
Δ = 632-4·21·(-2730)
Δ = 233289
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{233289}=483$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(63)-483}{2*21}=\frac{-546}{42}
=-13
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(63)+483}{2*21}=\frac{420}{42}
=10
$