-4=-9n^2

Solution for -4=-9n^2 equation:

-4=-9n^2

We move all terms to the left:

-4-(-9n^2)=0

We get rid of parentheses

9n^2-4=0

a = 9; b = 0; c = -4;
Δ = b2-4ac
Δ = 02-4·9·(-4)
Δ = 144
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{144}=12$
$n_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-12}{2*9}=\frac{-12}{18}
=-2/3
$
$n_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+12}{2*9}=\frac{12}{18}
=2/3
$