Simplify. Use only positive exponents:

$\displaystyle {z}^{{-{{4}}}}\cdot{z}^{{7}}$ Preview Question 1 Part 1 of 3  

$\displaystyle {r}^{{7}}\cdot{r}^{{-{{9}}}}$ Preview Question 1 Part 2 of 3  

$\displaystyle {y}^{{-{{7}}}}\cdot{y}^{{-{{2}}}}$ Preview Question 1 Part 3 of 3  

You may need to use parentheses around your denominator. For example $\displaystyle \frac{{1}}{{{2}{a}}}$ is entered as 1/(2a).