12=x+5x2

Solution for 12=x+5x2 equation:

12=x+5x^2

We move all terms to the left:

12-(x+5x^2)=0

We get rid of parentheses

-5x^2-x+12=0

We add all the numbers together, and all the variables

-5x^2-1x+12=0

a = -5; b = -1; c = +12;
Δ = b2-4ac
Δ = -12-4·(-5)·12
Δ = 241
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-1)-\sqrt{241}}{2*-5}=\frac{1-\sqrt{241}}{-10}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1)+\sqrt{241}}{2*-5}=\frac{1+\sqrt{241}}{-10}
$