Solve a^2=6561

$$a ^ { 2 } = 6561$$

Solve for a

$$a=81$$

$$a=-81$$

Steps Using Difference of Squares

Subtract 6561 from both sides.

$$a^{2}-6561=0$$

Consider a^{2}-6561. Rewrite a^{2}-6561 as a^{2}-81^{2}. The difference of squares can be factored using the rule: a^{2}-b^{2}=\left(a-b\right)\left(a+b\right).

$$\left(a-81\right)\left(a+81\right)=0$$

To find equation solutions, solve a-81=0 and a+81=0.

$$a=81 a=-81$$

Steps by Finding Square Root

Take the square root of both sides of the equation.

$$a=81 a=-81$$

Steps Using the Quadratic Formula

Subtract 6561 from both sides.

$$a^{2}-6561=0$$

This equation is in standard form: ax^{2}+bx+c=0. Substitute 1 for a, 0 for b, and -6561 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.

$$a=\frac{0±\sqrt{0^{2}-4\left(-6561\right)}}{2}$$

Square 0.

$$a=\frac{0±\sqrt{-4\left(-6561\right)}}{2}$$

Multiply -4 times -6561.

$$a=\frac{0±\sqrt{26244}}{2}$$

Take the square root of 26244.

$$a=\frac{0±162}{2}$$

Now solve the equation a=\frac{0±162}{2} when ± is plus. Divide 162 by 2.

$$a=81$$

Now solve the equation a=\frac{0±162}{2} when ± is minus. Divide -162 by 2.

$$a=-81$$

The equation is now solved.

$$a=81 a=-81$$