How do you find the non-permissable value?

Question

How? There is no info. on the internet!

Answer 1

The non-permissable value of what?

If we are talking about an mathematical/algebraic expression, one tip might be to look at the denominator of any division. Since division by 0 is undefined, any value that results in the denominator being 0 could be considered non-permissable.

Answer 2

The usual non-permissable value is the xalue of a pronumeral that results in division by zero
eg f(x) = 5x + 3/(2x-1)

Clearly 2x - 1 cannot equal zero so x = 1/2 is not permissable

In the real number field clearly the square root of a negative number is disallowed. the logarithm of a non-positive number is disallowed.

So one could ask
What valiues of x are permissable for √(x^2 - 5x + 6)
Well x^2 - 5x + 6 < 0 for 2 < x < 3 and the square root of a negaitve number is undefined in the field of real numbers.
Therefore the only permissable values of x (ie the DOMAIN of the function f(x) = √(x^2 - 5x + 6) ) are x ≤ 2 amd x ≥ 3

Similarly if y = log (x -5) then x - 5 must of necessity be positive in the field of real numbers.
ie x - 5 > 0 ie x > 5. This is the domain of this function

Answer 3

A non-permissible value is a value not allowable under the circumstances. Are you trying to find a non-permissable value to a certain question or problem? For example if a questions is asking for all rational numbers then an irrational number would be non-permissible. Another example is something that is a contradiction to your logic.