-7.2x(x-15.6)=-9

Solution for -7.2x(x-15.6)=-9 equation:

-7.2x(x-15.6)=-9

We move all terms to the left:

-7.2x(x-15.6)-(-9)=0

We add all the numbers together, and all the variables

-7.2x(x-15.6)+9=0

We multiply parentheses

-7x^2+109.2x+9=0

a = -7; b = 109.2; c = +9;
Δ = b2-4ac
Δ = 109.22-4·(-7)·9
Δ = 12176.64
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{-(109.2)-\sqrt{12176.64}}{2*-7}=\frac{-109.2-\sqrt{12176.64}}{-14}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(109.2)+\sqrt{12176.64}}{2*-7}=\frac{-109.2+\sqrt{12176.64}}{-14}
$