0.4x^2-7.2x=1

Solution for 0.4x^2-7.2x=1 equation:

0.4x^2-7.2x=1

We move all terms to the left:

0.4x^2-7.2x-(1)=0

a = 0.4; b = -7.2; c = -1;
Δ = b2-4ac
Δ = -7.22-4·0.4·(-1)
Δ = 53.44
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{-(-7.2)-\sqrt{53.44}}{2*0.4}=\frac{7.2-\sqrt{53.44}}{0.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-7.2)+\sqrt{53.44}}{2*0.4}=\frac{7.2+\sqrt{53.44}}{0.8}
$