40-(12X2)=a

Solution for 40-(12X2)=a equation:

40-(12X^2)=X

We move all terms to the left:

40-(12X^2)-(X)=0

We add all the numbers together, and all the variables

-12X^2-1X+40=0

a = -12; b = -1; c = +40;
Δ = b2-4ac
Δ = -12-4·(-12)·40
Δ = 1921
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{1921}}{2*-12}=\frac{1-\sqrt{1921}}{-24}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1)+\sqrt{1921}}{2*-12}=\frac{1+\sqrt{1921}}{-24}
$