Variable $x$ cannot be equal to $0$ since division by zero is not defined. Multiply both sides of the equation by $16x$, the least common multiple of $x,16$.
$$16\times 81=xx$$
Multiply $x$ and $x$ to get $x^{2}$.
$$16\times 81=x^{2}$$
Multiply $16$ and $81$ to get $1296$.
$$1296=x^{2}$$
Swap sides so that all variable terms are on the left hand side.
$$x^{2}=1296$$
Take the square root of both sides of the equation.
$$x=36$$ $$x=-36$$
Steps Using the Quadratic Formula
Variable $x$ cannot be equal to $0$ since division by zero is not defined. Multiply both sides of the equation by $16x$, the least common multiple of $x,16$.
$$16\times 81=xx$$
Multiply $x$ and $x$ to get $x^{2}$.
$$16\times 81=x^{2}$$
Multiply $16$ and $81$ to get $1296$.
$$1296=x^{2}$$
Swap sides so that all variable terms are on the left hand side.
$$x^{2}=1296$$
Subtract $1296$ from both sides.
$$x^{2}-1296=0$$
This equation is in standard form: $ax^{2}+bx+c=0$. Substitute $1$ for $a$, $0$ for $b$, and $-1296$ for $c$ in the quadratic formula, $\frac{-b±\sqrt{b^{2}-4ac}}{2a}$.
