Precalculus Examples

$81 = a^{2}$

Step 1

Rewrite the equation as $a^{2} = 81$ .

$a^{2} = 81$

Step 2

Take the specified root of both sides of the equation to eliminate the exponent on the left side.

$a = \pm \sqrt{81}$

Step 3

Simplify $\pm \sqrt{81}$ .

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Step 3.1

Rewrite $81$ as $9^{2}$ .

$a = \pm \sqrt{9^{2}}$

Step 3.2

Pull terms out from under the radical, assuming positive real numbers.

$a = \pm 9$

Step 4

The complete solution is the result of both the positive and negative portions of the solution.

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Step 4.1

First, use the positive value of the $\pm$ to find the first solution.

$a = 9$

Step 4.2

Next, use the negative value of the $\pm$ to find the second solution.

$a = - 9$

Step 4.3

The complete solution is the result of both the positive and negative portions of the solution.

$a = 9, - 9$