87=X*2x

Solution for 87=X*2x equation:

87=X*2X

We move all terms to the left:

87-(X*2X)=0

We add all the numbers together, and all the variables

-(+X*2X)+87=0

We get rid of parentheses

-X*2X+87=0

Wy multiply elements

-2X^2+87=0

a = -2; b = 0; c = +87;
Δ = b2-4ac
Δ = 02-4·(-2)·87
Δ = 696
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:

$\sqrt{\Delta}=\sqrt{696}=\sqrt{4*174}=\sqrt{4}*\sqrt{174}=2\sqrt{174}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-2\sqrt{174}}{2*-2}=\frac{0-2\sqrt{174}}{-4}
=-\frac{2\sqrt{174}}{-4}
=-\frac{\sqrt{174}}{-2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+2\sqrt{174}}{2*-2}=\frac{0+2\sqrt{174}}{-4}
=\frac{2\sqrt{174}}{-4}
=\frac{\sqrt{174}}{-2}
$