(a*10)*(a/10)=200

Solution for (a*10)*(a/10)=200 equation:

(a*10)(a/10)=200

We move all terms to the left:

(a*10)(a/10)-(200)=0

We add all the numbers together, and all the variables

(+a*10)(+a/10)-200=0

We multiply parentheses ..

(+10a^2)-200=0

We get rid of parentheses

10a^2-200=0

a = 10; b = 0; c = -200;
Δ = b2-4ac
Δ = 02-4·10·(-200)
Δ = 8000
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{8000}=\sqrt{1600*5}=\sqrt{1600}*\sqrt{5}=40\sqrt{5}$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-40\sqrt{5}}{2*10}=\frac{0-40\sqrt{5}}{20}
=-\frac{40\sqrt{5}}{20}
=-2\sqrt{5}
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+40\sqrt{5}}{2*10}=\frac{0+40\sqrt{5}}{20}
=\frac{40\sqrt{5}}{20}
=2\sqrt{5}
$