x^2+1.2x+0.36=0.64

Solution for x^2+1.2x+0.36=0.64 equation:

x^2+1.2x+0.36=0.64

We move all terms to the left:

x^2+1.2x+0.36-(0.64)=0

We add all the numbers together, and all the variables

x^2+1.2x-0.28=0

a = 1; b = 1.2; c = -0.28;
Δ = b2-4ac
Δ = 1.22-4·1·(-0.28)
Δ = 2.56
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{-(1.2)-\sqrt{2.56}}{2*1}=\frac{-1.2-\sqrt{2.56}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1.2)+\sqrt{2.56}}{2*1}=\frac{-1.2+\sqrt{2.56}}{2}
$