(3x+1)(x-2)=0.

Solution for (3x+1)(x-2)=0. equation:

(3x+1)(x-2)=0.

We multiply parentheses ..

(+3x^2-6x+x-2)=0

We get rid of parentheses

3x^2-6x+x-2=0

We add all the numbers together, and all the variables

3x^2-5x-2=0

a = 3; b = -5; c = -2;
Δ = b2-4ac
Δ = -52-4·3·(-2)
Δ = 49
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{49}=7$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-5)-7}{2*3}=\frac{-2}{6}
=-1/3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5)+7}{2*3}=\frac{12}{6}
=2
$