0=-0.04x^2+7.1x+7.2

Solution for 0=-0.04x^2+7.1x+7.2 equation:

0=-0.04x^2+7.1x+7.2

We move all terms to the left:

0-(-0.04x^2+7.1x+7.2)=0

We add all the numbers together, and all the variables

-(-0.04x^2+7.1x+7.2)=0

We get rid of parentheses

0.04x^2-7.1x-7.2=0

a = 0.04; b = -7.1; c = -7.2;
Δ = b2-4ac
Δ = -7.12-4·0.04·(-7.2)
Δ = 51.562
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{-(-7.1)-\sqrt{51.562}}{2*0.04}=\frac{7.1-\sqrt{51.562}}{0.08}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-7.1)+\sqrt{51.562}}{2*0.04}=\frac{7.1+\sqrt{51.562}}{0.08}
$