Sunday, 18 September 2016

calculus - Finding limxto2fracx+2sqrtx11; without L'Hospital



I have been trying to find
lim
without L'Hospital's Rule, but I am stuck.
I tried




  • Rationalizationg the denominator


  • Factoring out \,x



But it did not work. Finally, I used L'Hospital's Theorem and I got the answer -2.
Is there any way to evaluate this without this concept?


Answer



Rationalizing the denominator works.



\lim_{x\to -2}{\frac{x+2}{\sqrt{-x-1}-1}}=\lim_{x\to -2}{\frac{x+2}{\sqrt{-x-1}-1}}.\frac{{\sqrt{-x-1}+1}}{{\sqrt{-x-1}+1}}=\lim_{x\to -2}{\frac{x+2}{-x-2}}.{(\sqrt{-x-1}+1)}=\lim_{x\to -2}-{(\sqrt{-x-1}+1)}=-2


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