1080=1000+1000r(2)

Solution for 1080=1000+1000r(2) equation:

1080=1000+1000r(2)

We move all terms to the left:

1080-(1000+1000r(2))=0

We add all the numbers together, and all the variables

-(+1000r^2+1000)+1080=0

We get rid of parentheses

-1000r^2-1000+1080=0

We add all the numbers together, and all the variables

-1000r^2+80=0

a = -1000; b = 0; c = +80;
Δ = b2-4ac
Δ = 02-4·(-1000)·80
Δ = 320000
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{320000}=\sqrt{160000*2}=\sqrt{160000}*\sqrt{2}=400\sqrt{2}$
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-400\sqrt{2}}{2*-1000}=\frac{0-400\sqrt{2}}{-2000}
=-\frac{400\sqrt{2}}{-2000}
=-\frac{\sqrt{2}}{-5}
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+400\sqrt{2}}{2*-1000}=\frac{0+400\sqrt{2}}{-2000}
=\frac{400\sqrt{2}}{-2000}
=\frac{\sqrt{2}}{-5}
$