Math, asked by nowshin35, 1 year ago

Why we don't use negative base in logarithm? ​


VedaantArya: Using a negative base in logarithms:
By definition, you'd know that a^b = c, implies log of c to the base a is b.
Now, if a were negative, say (by your example, if you don't mind) -2, (-2)^b = c, implies log of c to the base (-2) is b.

But consider these:
(-2)^2 = 4. (2)^2 = 4.
Okay, it isn't a major problem...
VedaantArya: ...But consider this:
(-2)^x = 3.
What's x? That is, what power of -2 could give you 3?
You'll either have no answer, or you'll say that it should be the same as the power of 2 that would give you 3.
But that power would be fractional.
And that, is a problem, because a fractional power of a negative number may not be a real number.
VedaantArya: The square root (that is, the 0.5-th power) of -1 isn't real (it's called iota, and an imaginary number), and this should be intuitively understand-able, that no real number on multiplying it by itself could possibly give a negative real number, since - * - = +, and + * + = +.
VedaantArya: So is the case with other fractional powers of negative numbers.
The logarithms of non-simple numbers to a negative base can't be defined real-ly, so. Yeah. We just take them out of the equation altogether.
If you still don't get it, comment below.
nowshin35: Thanks
nowshin35: I understand it clearly

Answers

Answered by Khushwant23
2
log of negative base is not defined.
it is due to if you will notice the graph of log x when its value on x axis does not crosses the origin in the negative side therefore it is not defined for the negative base
Attachments:

nowshin35: but we can write (-2)^3,then we say log-2 (-8)= -3 undefined ?
nowshin35: log-2 (-8)=3*
Khushwant23: the domain of logarithm doesn't allow negative value in its base you can check the graph
nowshin35: thanks
Answered by brunoconti
0

Answer:

Step-by-step explanation:

the logarithm function is defined Only for strictly positive numbers.


nowshin35: my ques is why it is undefined?
brunoconti: Think of square root of x which is Only defined for x >= 0. this is the same. there are some functions that are Only defined for positive numbers. however in the complex plane u can use negative numbers
nowshin35: thanks a lot
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