x-x*0.04x=65000

Solution for x-x*0.04x=65000 equation:

x-x*0.04x=65000

We move all terms to the left:

x-x*0.04x-(65000)=0

Wy multiply elements

0x^2+x-65000=0

We add all the numbers together, and all the variables

x^2+x-65000=0

a = 1; b = 1; c = -65000;
Δ = b2-4ac
Δ = 12-4·1·(-65000)
Δ = 260001
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{260001}=\sqrt{9*28889}=\sqrt{9}*\sqrt{28889}=3\sqrt{28889}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(1)-3\sqrt{28889}}{2*1}=\frac{-1-3\sqrt{28889}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+3\sqrt{28889}}{2*1}=\frac{-1+3\sqrt{28889}}{2}
$