Limit

Limit

Postby nycmath » Wed Aug 19, 2026 5:36 am

See attachment. Enjoy.
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Re: Limit

Postby Math Tutor » Wed Aug 19, 2026 6:01 am

Factor the numerator as a difference of squares: [tex]x-9=(\sqrt{x}-3)(\sqrt{x}+3)[/tex].

For [tex]x \neq 9[/tex] the factor [tex]\sqrt{x}-3[/tex] cancels:

[tex]\frac{x-9}{\sqrt{x}-3}=\frac{(\sqrt{x}-3)(\sqrt{x}+3)}{\sqrt{x}-3}=\sqrt{x}+3[/tex]

Hence [tex]\lim_{x \to 9}\frac{x-9}{\sqrt{x}-3}=\sqrt{9}+3=6[/tex].

(Same thing: multiply top and bottom by the conjugate [tex]\sqrt{x}+3[/tex].)

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Re: Limit

Postby Eigenvalue » Wed Aug 19, 2026 7:49 am

[tex]\lim_{x \to 9}x[sqrt(x)+3]
=[tex]\sqrt{9}[/tex]+3=6

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Re: Limit

Postby nycmath » Thu Aug 20, 2026 8:11 am

Math Tutor wrote:Factor the numerator as a difference of squares: [tex]x-9=(\sqrt{x}-3)(\sqrt{x}+3)[/tex].

For [tex]x \neq 9[/tex] the factor [tex]\sqrt{x}-3[/tex] cancels:

[tex]\frac{x-9}{\sqrt{x}-3}=\frac{(\sqrt{x}-3)(\sqrt{x}+3)}{\sqrt{x}-3}=\sqrt{x}+3[/tex]

Hence [tex]\lim_{x \to 9}\frac{x-9}{\sqrt{x}-3}=\sqrt{9}+3=6[/tex].

(Same thing: multiply top and bottom by the conjugate [tex]\sqrt{x}+3[/tex].)


Pretty easy and straightforward.

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Re: Limit

Postby nycmath » Thu Aug 20, 2026 8:12 am

Eigenvalue wrote:[tex]\lim_{x \to 9}x[sqrt(x)+3]
=[tex]\sqrt{9}[/tex]+3=6


Correct but please edit your LaTex.

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