(X-1.2)(x+3.3)=0

Solution for (X-1.2)(x+3.3)=0 equation:

(X-1.2)(X+3.3)=0

We multiply parentheses ..

(+X^2+3.3X-1.2X-3.96)=0

We get rid of parentheses

X^2+3.3X-1.2X-3.96=0

We add all the numbers together, and all the variables

X^2+2.1X-3.96=0

a = 1; b = 2.1; c = -3.96;
Δ = b2-4ac
Δ = 2.12-4·1·(-3.96)
Δ = 20.25
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(2.1)-\sqrt{20.25}}{2*1}=\frac{-2.1-\sqrt{20.25}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(2.1)+\sqrt{20.25}}{2*1}=\frac{-2.1+\sqrt{20.25}}{2}
$