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Mathematics 19 Online
OpenStudy (anonymous):

Can someone teach me how to find the domain of an expression: sqrt(x(x-2))

OpenStudy (amistre64):

sqrt(a) is valid for all positive a values

OpenStudy (amistre64):

so whatever makes the innards go less than zero is bad

OpenStudy (anonymous):

Since it is a sqrt, you cannot have your value inside to be a negative. So, this means that your x(x-2) >= 0

OpenStudy (anonymous):

I plotted this function and I got:

OpenStudy (amistre64):

that looks about right; since you got a quadratic in there its gonna act wierd like that

OpenStudy (amistre64):

at 0 and 2 we have roots <...........0.........2.........> - + + - - + ------------------- + - + Domain: (-inf,0] or [2,inf)

OpenStudy (anonymous):

can you show the work, please?

OpenStudy (amistre64):

that is the work

OpenStudy (anonymous):

the formulas. Analitically

OpenStudy (anonymous):

Im really good at finding the domain graphically

OpenStudy (amistre64):

sqrt[x(x-2)] is already factored out .... i really cant see much else to do with it other than plot it on a number line and show the +- ranges

OpenStudy (amistre64):

x = 0 when x = 0 x-2 = 0 when x = 2

OpenStudy (anonymous):

x>=0 x>=2 both inequalities are true

OpenStudy (amistre64):

<...................0.................2................> x<0; - x>0; + + x<2; - - x>2; + ------------------------------------- -*- = + +*-=- +*+=+

OpenStudy (amistre64):

Domain: (-inf,0] or [2,inf)

OpenStudy (anonymous):

ahhh got it

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