Hello,Originally Posted byOReilly

I'll try to explain by an example:

Take

a) f(1)=-2 and f(2)=4. That means between x=1 and x=2 the graph of the "function" has to cross the x-axis. But you'll never get the result 0 (zero), if the base isn't zero too.

b) which isn't a real number.

To avoid all these difficulties exponential functions are only defined for positive bases except 1.

Greetings

EB