My Math Forum Help me with 2 Lim tasks

 Pre-Calculus Pre-Calculus Math Forum

November 18th, 2017, 07:06 AM   #1
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Help me with 2 Lim tasks

Hello there. Could someone help me, and explain how these 2 tasks should be done. I added them in attachment. I know how to do simple lim tasks, but these ones are more complicated and I'm really not best at math.

Thank You.
Attached Images
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 November 18th, 2017, 07:25 AM #2 Global Moderator   Joined: Dec 2006 Posts: 19,183 Thanks: 1647 The first limit is easily found by use of de l'Hôpital's rule. For a proof that doesn't rely on calculus, the method suggested by v8archie below is best. Thanks from topsquark and v8archie Last edited by skipjack; November 18th, 2017 at 08:30 AM.
 November 18th, 2017, 07:32 AM #3 Math Team   Joined: Dec 2013 From: Colombia Posts: 7,330 Thanks: 2457 Math Focus: Mainly analysis and algebra First one: multiply by $$\frac{\sqrt{7+4x}+\sqrt{7-x}}{\sqrt{7+4x}+\sqrt{7-x}} \cdot \frac{\sqrt{3+x}+\sqrt{3+2x}}{\sqrt{3+x}+\sqrt{3+2 x}}$$ Second one: write $2x-1=1+2(x-1)$ and use $$\lim_{t \to 0} (1+at)^{\frac1t}=e^a$$ Thanks from topsquark

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