Evaluate (-6)^-21*(-6)^18

${(- 6)}^{- 21} \cdot {(- 6)}^{18}$

Multiply ${(- 6)}^{- 21}$ by ${(- 6)}^{18}$ by adding the exponents.

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

${(- 6)}^{- 21 + 18}$

Add $- 21$ and $18$ .

${(- 6)}^{- 3}$

Rewrite the expression using the negative exponent rule $b^{- n} = \frac{1}{b^{n}}$ .

$\frac{1}{{(- 6)}^{3}}$

Raise $- 6$ to the power of $3$ .

$\frac{1}{- 216}$

Move the negative in front of the fraction.

$- \frac{1}{216}$

The result can be shown in multiple forms.

Exact Form:

$- \frac{1}{216}$

Decimal Form:

$- 0.004\overline{629}$