15n^2=21n

Solution for 15n^2=21n equation:

15n^2=21n

We move all terms to the left:

15n^2-(21n)=0

a = 15; b = -21; c = 0;
Δ = b2-4ac
Δ = -212-4·15·0
Δ = 441
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{441}=21$
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-21)-21}{2*15}=\frac{0}{30}
=0
$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-21)+21}{2*15}=\frac{42}{30}
=1+2/5
$