Why when indices cancelled out leave 1 at top? This is a really basic question, but I have just got interested in math and learning rules about powers/indices and this confused me a little.
$\dfrac{a^3}{a^7}$ after they cancel out we get $\dfrac{1}{a^4}$
My question is why do we have 1 remain at the top? Why not 0, any simple explanation for this?

It is really $a^{3-3}=a^0=1$...
