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Math Help - Find the domain of the expression.

  1. #1
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    Find the domain of the expression.

    Can you help me find the domain of these expressions?

    1.) -x^4+x^3+9x

    2.) 2r^2-5/3r+6

    3.) 1/sqrt(x-1)
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  2. #2
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    Quote Originally Posted by DHS1 View Post
    Can you help me find the domain of these expressions?

    1.) -x^4+x^3+9x

    2.) 2r^2-5/3r+6

    3.) 1/sqrt(x-1)
    Does 5/3r mean 5/(3r) or (5/3)r?

    For domain questions such as these, remember: division by zero is undefined, and square root of a negative number is not in reals.
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  3. #3
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    Quote Originally Posted by undefined View Post
    Does 5/3r mean 5/(3r) or (5/3)r?

    For domain questions such as these, remember: division by zero is undefined, and square root of a negative number is not in reals.
    Thank you. However I do know what you just said, I just can't figure those three problems out. And I meant (2r^2-5)/(3r+6)
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  4. #4
    MHF Contributor undefined's Avatar
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    Quote Originally Posted by DHS1 View Post
    Thank you. However I do know what you just said, I just can't figure those three problems out. And I meant (2r^2-5)/(3r+6)
    1) All reals
    2) Solve the inequality 3r+6 \ne 0
    3) Solve the inequality x - 1 > 0
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