anonymous 4 years ago Simplify 3^-9 / 3^-12

1. anonymous

answers: 3^3 3^21 1/3^21 1/3^3

2. asnaseer

do you know the rule:$x^a/x^b=x^{a-b}$

3. anonymous

nope sure dont

4. asnaseer

what have you been taught about indexes?

5. anonymous

nothing at all that i can recall

6. anonymous

no pun intended

7. asnaseer

so how do they expect you to solve this? have you been told to use any specific method?

8. anonymous

i think we have i just dont remember

9. asnaseer

well at the very least you need to know the rules of index multiplication and division.

10. anonymous

prolly do just dont remember what they are

11. asnaseer

e.g. the rule I just showed you can be proved with following example:$\frac{x^5}{x^3}=\frac{x*x*x*x*x}{x*x*x}=x*x=x^2$

12. anonymous

oooo thtz right i remember now thx

13. asnaseer

so in your case,$3^{-9}/3^{-12}=3^{-9-(-12)}=3^{-9+12}=3^3$

14. anonymous

yup i got it thanks alot

15. asnaseer

yw