## greeneyes<3 2 years ago Find the domain of the expression: 1. 6x^2-9, x>0 2. (x^2-x-12)/(x^2-8+16) Please show steps or explain them to me! Thank you!

1. munaali

-9

2. greeneyes<3

is it like all real numbers, or can you please explain?

3. munaali

yes

4. greeneyes<3

it still does not make sense, x has to be > 0

5. munaali

the real numer has negive

6. greeneyes<3

@jim_thompson5910 can you help me with these two problems?

7. jim_thompson5910

by default, all polynomials have a domain of the set of all real numbers

8. jim_thompson5910

but because it clearly states that x > 0, that means the domain is x > 0, so the domain is the set of positive real numbers

9. jim_thompson5910

to find the domain of (x^2-x-12)/(x^2-8x+16), set the denominator equal to zero and solve for x those two solutions will be values you exclude from the domain

10. greeneyes<3

Thank you! Now my answers are: 1. x=all + real numbers 2. x cannot=+ or - 4, and -2 is that right?

11. jim_thompson5910

the first one is correct, but the second is not

12. jim_thompson5910

hint: x^2 - 8x + 16 factors to (x-4)(x-4)

13. greeneyes<3

so x cannot equal 4, or -2 ?

14. jim_thompson5910

how are you getting -2?

15. greeneyes<3

oh nevermind I see what I was doing wrong, was separating x^2 and -8x and solving them each for -16 separately. So the answer is just x cannot = 4 ?

16. jim_thompson5910

bingo, the domain is the set of all real numbers but x cannot equal 4

17. greeneyes<3

Okay thank you! :)

18. jim_thompson5910

you're welcome

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