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anonymous
 5 years ago
How do I: Express the domain of the given function using interval notation?
f(x)=x/ 15x^2 + 13x  20
anonymous
 5 years ago
How do I: Express the domain of the given function using interval notation? f(x)=x/ 15x^2 + 13x  20

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anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0hey. do you mean f(x) = x / (15x^2 + 13x  20) ?

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0nevermind i solved it thanks

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0i meant to ask a different question, sorry

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0is there another question you want to ask?

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0yes. it was determine domain and range using interval notation of f(x)= radicand(x^2 8x 9

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0\[f(x) = \sqrt{x^2 8x 9}\]

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0just so you know i believe radicand refers to what is under the square root, but you mean square root of (x^2 8x 9) right?

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0ok well for a square root function what you need to know is that what's under the square root can't be negative, because no real number multiplied by itself equals a negative

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0ok i understand so far

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0ok, so you want to try to factor that, to see where it is negative and where it is positive. you did the other problem so you know how to factor, right?

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0yes, i have x=9 and x=1

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0that's not quite right, look at it again

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0is it 9 and 1 instead?

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0sorry, my browser crashed. yes, that's right. so you have sqrt ((x9)(x+1)). what i like to do is draw a number line below that to help me see where the function is 0, negative, and positive

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0so draw a line, hashmarks at 1 and 9, and we know it's 0 at those points, so mark 0 above 1 and 9

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0now test a point on the left side, in the middle, and on the right to see if it comes up positive or negative

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0try x= 2. (29)(2+1) is a negative times a negative, so that's positive. so now i mark all +++ to the left of the first 0 on my line

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0you still here, is this helping?

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0im here thank you. how do you know what sign to use when determining if the equation is true?

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0what i mean is, you plug in 2 to the equation to see if its true right?

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0what do you mean by true?

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0(2)^2  8(2) 9=0 ?

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0or do you use an equality sign

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0no, we already know that the values that make what's under the square root equal to 0 are x = 1 and x = 9

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0that's what the factoring is for

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0by plugging in 2, we just want to see if that section of xvalues comes up negative for y or positive

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0remember the goal is to see which xvalues make what's under the square root negative, because those are not part of the domain

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0so by plugging in 2, we get 11. then what from there?

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0it doesn't matter what the number is, we just care that it's positive, so did you draw the number line like i said? do you understand what i mean by that?

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0so since they're both positive, that means what for interval notation?

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0well 2 turned out positive, so that means that all values less than 1 turn out positive, so those will be part of the domain

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0but we still have to check the other intervals

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0the one in the middle comes out negative

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0and the last one comes out positive

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0yes that's right, so the domain is the positive part

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0ok so what does it look like in interval form?

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0ok (inf, 1) U (9, inf) is what it will be

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0(infinity,1] [9,infinity)? something like that?

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0the brackets are right. (inf, 1] U [9, inf) the U stands for union

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0got it! thank you for your help!
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