How do i find the restrictions of domain or range on this function?

Question

amistre64 · Answer

retrictions are what makes things go bad for a domain, or what we cannot obtain for a range

undeadknight26 · Answer

y = -4x + 6

For this i said the restriction of the domain would be -4?

amistre64 · Answer

why would -4 make this go bad?

undeadknight26 · Answer

Now that you say it...I dunno o.o

undeadknight26 · Answer

I have no idea how to find the restrictions on a function...I cannot find it in my lesson either and even asked a few friends.

amistre64 · Answer

can you think of anything that would make it go bad?  is there a divide by zero possibility? a negative even root? logs of 0? etc ...

undeadknight26 · Answer

No there are none of those showing it has no restrictions?

amistre64 · Answer

for example:  1/sqrt(ln(x))

we have to restrict some values of x to make this thing deifnable

amistre64 · Answer

-4x+6 has no restrictions, its a continuous line

undeadknight26 · Answer

Okay...So can can you give me an example of an equation with an restriction?

amistre64 · Answer

1/sqrt(ln(x))

amistre64 · Answer

we cant divide by zero so sqrt(ln(x)) needs to not be zero

ln(x) is only defined for x bigger than 0 sooo

ln(x) >= 0 is what we need to account for,  this is good for x>=1

amistre64 · Answer

opps, x > 1 since ln(1)=0

amistre64 · Answer

you need to know what is forbidden in math in order to develop a sense for what cant be done with certain values of x

anonymous · Answer

Example:
$$y=\frac{ 2 }{ x-1 }$$
$$x-1\neq0$$
$$x \neq1$$

anonymous · Answer

Another one:
$$y=\sqrt{x+3}$$
$$x+3\ge0$$
$$x \ge-3$$

anonymous · Answer

Anything less than -3 will make this function undefined.

undeadknight26 · Answer

Thank you both :D