(3x+1)x=30

Solution for (3x+1)x=30 equation:

(3x+1)x=30

We move all terms to the left:

(3x+1)x-(30)=0

We multiply parentheses

3x^2+x-30=0

a = 3; b = 1; c = -30;
Δ = b2-4ac
Δ = 12-4·3·(-30)
Δ = 361
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{361}=19$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(1)-19}{2*3}=\frac{-20}{6}
=-3+1/3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+19}{2*3}=\frac{18}{6}
=3
$