Precalculus Examples

$9^{x - 1} = 81$

Step 1

Create equivalent expressions in the equation that all have equal bases.

$9^{x - 1} = 9^{2}$

Step 2

Since the bases are the same, then two expressions are only equal if the exponents are also equal.

$x - 1 = 2$

Step 3

Move all terms not containing $x$ to the right side of the equation.

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Step 3.1

Add $1$ to both sides of the equation.

$x = 2 + 1$

Step 3.2

Add $2$ and $1$ .

$x = 3$