# [SOLVED]f(x)=ab^{x} where b must be a positive real number

#### Avalance789

##### New member
Quote: "In mathematics, an exponential function is a function of the form

f(x)=ab^{x}

where b is a POSITIVE REAL number"

Wait. Give me a reason, why exponent base must be positive and real?

What happens if b<0?

#### topsquark

##### Well-known member
MHB Math Helper
Quote: "In mathematics, an exponential function is a function of the form

f(x)=ab^{x}

where b is a POSITIVE REAL number"

Wait. Give me a reason, why exponent base must be positive and real?

What happens if b<0?
What happens if b = -1 and x = 1/2?

-Dan

#### Avalance789

##### New member
It means sqrt{-1}?

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MHB Math Helper

#### topsquark

##### Well-known member
MHB Math Helper
It means sqrt{-1}?

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Exactly. And as i is not real number we can't use it for what you seem to be working with.

-Dan

#### Avalance789

##### New member
Ok, got it. So from this point we get into complex numbers.

Thank you!

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