12-1/5r=2r

Solution for 12-1/5r=2r equation:

12-1/5r=2r

We move all terms to the left:

12-1/5r-(2r)=0


Domain of the equation: 5r!=0

r!=0/5

r!=0

r∈R


We add all the numbers together, and all the variables

-2r-1/5r+12=0

We multiply all the terms by the denominator


-2r*5r+12*5r-1=0

Wy multiply elements

-10r^2+60r-1=0

a = -10; b = 60; c = -1;
Δ = b2-4ac
Δ = 602-4·(-10)·(-1)
Δ = 3560
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:

$\sqrt{\Delta}=\sqrt{3560}=\sqrt{4*890}=\sqrt{4}*\sqrt{890}=2\sqrt{890}$
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(60)-2\sqrt{890}}{2*-10}=\frac{-60-2\sqrt{890}}{-20}
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(60)+2\sqrt{890}}{2*-10}=\frac{-60+2\sqrt{890}}{-20}
$