1,2x(1,8x-3,8)=4,25

Solution for 1,2x(1,8x-3,8)=4,25 equation:

1.2x(1.8x-3.8)=4.25

We move all terms to the left:

1.2x(1.8x-3.8)-(4.25)=0

We add all the numbers together, and all the variables

1.2x(1.8x-3.8)-4.25=0

We multiply parentheses

x^2-3.8x-4.25=0

a = 1; b = -3.8; c = -4.25;
Δ = b2-4ac
Δ = -3.82-4·1·(-4.25)
Δ = 31.44
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{-(-3.8)-\sqrt{31.44}}{2*1}=\frac{3.8-\sqrt{31.44}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-3.8)+\sqrt{31.44}}{2*1}=\frac{3.8+\sqrt{31.44}}{2}
$