2+21a=1a^2

Solution for 2+21a=1a^2 equation:

2+21a=1a^2

We move all terms to the left:

2+21a-(1a^2)=0

determiningTheFunctionDomain
-1a^2+21a+2=0

a = -1; b = 21; c = +2;
Δ = b2-4ac
Δ = 212-4·(-1)·2
Δ = 449
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(21)-\sqrt{449}}{2*-1}=\frac{-21-\sqrt{449}}{-2}
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(21)+\sqrt{449}}{2*-1}=\frac{-21+\sqrt{449}}{-2}
$