Simplify 15^-4
------
15^5

Question

Simplify 15^-4
            ------
              15^5

anonymous · Answer

its a fraction

kinggeorge · Answer

Fractions are almost the same thing as multiplying. Instead, $$\Large {a^b \over a^c}=a^{b-c}$$Using ths same principles as the last problem, and this new information, what do you think it is?

anonymous · Answer

15^-11

anonymous · Answer

15^-9
is wut i ment

kinggeorge · Answer

Precisely!$$\large {15^{-4} \over 15^5}=15^{-4-5}=15^{-9}$$

kinggeorge · Answer

Are you supposed to simplify to positive exponents?

anonymous · Answer

no it ses siplify the fraction....but  15^-9 isnt an anser

kinggeorge · Answer

Is $$1\over15^9$$an answer?

anonymous · Answer

yep..but how would it go from -9 to +9

kinggeorge · Answer

There's one more rule for exponents that's very important. $$\large a^{-b}={1 \over a^b}$$This is how you would switch between positive/negative exponents.

anonymous · Answer

ok.. so when u X u add and when u / u subtract..?

kinggeorge · Answer

Exactly.

anonymous · Answer

so wut if u had to subtract but there were 2 / ansers?

kinggeorge · Answer

What do you mean?

anonymous · Answer

In which expression should the exponents be subtracted? 

(6^10)^-7
2^9/5^9
(-1/2)^11 X (-1/2)^-4
3^8/3^5

kinggeorge · Answer

Only in the last one. The first option involves something we haven't gone over yet here, in the second option there are different base numbers, and in the third we have to add the numbers.

In the fourth option, we have the right form, and the same base in both numbers.

anonymous · Answer

so it would be the last one?

kinggeorge · Answer

yes.

anonymous · Answer

kool