x*(x-0.3)=9

Solution for x*(x-0.3)=9 equation:

x(x-0.3)=9

We move all terms to the left:

x(x-0.3)-(9)=0

We multiply parentheses

x^2-0.3x-9=0

a = 1; b = -0.3; c = -9;
Δ = b2-4ac
Δ = -0.32-4·1·(-9)
Δ = 36.09
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{-(-0.3)-\sqrt{36.09}}{2*1}=\frac{0.3-\sqrt{36.09}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-0.3)+\sqrt{36.09}}{2*1}=\frac{0.3+\sqrt{36.09}}{2}
$