Find the domain of the function

[kebstein]

hi this is my first time here. i have just been admitted to the university of the gambia last month. i have a problem with this question. please i need help

find the domain
f is such that x maps to 1 all over the squareroot of x²-10x+12.

 

[CompuChip]

I assume you meant
f: x \mapsto \frac{1}{\sqrt{x^2 - 10x + 12}}.

What is the definition of domain? How would you go about finding it?

 

[kebstein]

yeah this is what i meant,

 

[CompuChip]

OK, so can you show us some attempt / ideas you had (no matter how stupid you think they are)? You completely ignored the template that pops up when posting a question, but it's there for a good reason. We are not too good at guessing what you do and don't know; moreover the idea is we just help you find the answer yourself, instead of just giving it to you.

 

[HallsofIvy]

you were asked before, what is the definition of "domain". If you know that definition, please tell us what it is. If you don't, look it up! You can't hope to do problems involving words you don't know!

 

[kebstein]

there is an error in my first question. it should
f: x mapsto frac{1}{\\sqrt{x^2 - 10x + 21}')

 

[kebstein]

i think i have to factorize x²-10+21
x²-3x-7x+21
x(x-3)-7(x-3)
(x-3) (x-7)

x-3 is greater than or equal to 0 and x-7 is greater than or equal 0
there for x is greater than or equal to 3 and x is greater than or equal to7

then Df = [3; 7]

is this correct