9z^2=21z

Solution for 9z^2=21z equation:

9z^2=21z

We move all terms to the left:

9z^2-(21z)=0

a = 9; b = -21; c = 0;
Δ = b2-4ac
Δ = -212-4·9·0
Δ = 441
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$z_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$z_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{441}=21$
$z_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-21)-21}{2*9}=\frac{0}{18}
=0
$
$z_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-21)+21}{2*9}=\frac{42}{18}
=2+1/3
$