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n-\frac{90}{n}=0
Subtract \frac{90}{n} from both sides.
\frac{nn}{n}-\frac{90}{n}=0
To add or subtract expressions, expand them to make their denominators the same. Multiply n times \frac{n}{n}.
\frac{nn-90}{n}=0
Since \frac{nn}{n} and \frac{90}{n} have the same denominator, subtract them by subtracting their numerators.
\frac{n^{2}-90}{n}=0
Do the multiplications in nn-90.
n^{2}-90=0
Variable n cannot be equal to 0 since division by zero is not defined. Multiply both sides of the equation by n.
n^{2}=90
Add 90 to both sides. Anything plus zero gives itself.
n=3\sqrt{10} n=-3\sqrt{10}
Take the square root of both sides of the equation.
n-\frac{90}{n}=0
Subtract \frac{90}{n} from both sides.
\frac{nn}{n}-\frac{90}{n}=0
To add or subtract expressions, expand them to make their denominators the same. Multiply n times \frac{n}{n}.
\frac{nn-90}{n}=0
Since \frac{nn}{n} and \frac{90}{n} have the same denominator, subtract them by subtracting their numerators.
\frac{n^{2}-90}{n}=0
Do the multiplications in nn-90.
n^{2}-90=0
Variable n cannot be equal to 0 since division by zero is not defined. Multiply both sides of the equation by n.
n=\frac{0±\sqrt{0^{2}-4\left(-90\right)}}{2}
This equation is in standard form: ax^{2}+bx+c=0. Substitute 1 for a, 0 for b, and -90 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.
n=\frac{0±\sqrt{-4\left(-90\right)}}{2}
Square 0.
n=\frac{0±\sqrt{360}}{2}
Multiply -4 times -90.
n=\frac{0±6\sqrt{10}}{2}
Take the square root of 360.
n=3\sqrt{10}
Now solve the equation n=\frac{0±6\sqrt{10}}{2} when ± is plus.
n=-3\sqrt{10}
Now solve the equation n=\frac{0±6\sqrt{10}}{2} when ± is minus.
n=3\sqrt{10} n=-3\sqrt{10}
The equation is now solved.