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Problems in Mathematical Analysis.pdf - pwp.net.ipl.pt

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Sec. 3]<br />

179. Hm (Vn + 1 \f~n).<br />

n -+ <<br />

-o/% i<br />

180. lim<br />

/<br />

Limits<br />

When seek<strong>in</strong>g the limit of a ratio of two <strong>in</strong>tegral polynomials<br />

6<br />

<strong>in</strong> * as<br />

x -+ oo, it is useful first to divide both terms of the ratio by xn , where n is<br />

the highest decree of these polynomials.<br />

A similar procedure is also possible <strong>in</strong> many cases for fractions conta<strong>in</strong><strong>in</strong>g<br />

irrational terms.<br />

Example 1.<br />

lim J2^-3)(3t-f^)(4A'-6) _<br />

Example 2.<br />

lim .<br />

*<br />

=. lim J = 1.<br />

181. lim ^rrr. *86. lim ^~~^=J.<br />

r -. or * ~' 1<br />

* + V X* -\-<br />

\<br />

182. lim ^^. 187. lim<br />

00 * jc<br />

-11-<br />

1/<br />

183. lim ., J" .<br />

.<br />

3* 188. lim<br />

+ 7<br />

184. lim 4-<br />

O ^2 Y L<br />

h<br />

^<br />

->* 10-j- A:<br />

3<br />

8v +5* 189. lirn<br />

185. lim -r-r~c<br />

-<br />

* ^ 5<br />

190. lim<br />

__ .<br />

Vx + Vx<br />

If P(A-) and Q (x) are <strong>in</strong>tegral polynomials and P (u) + or Q (a)<br />

then the limit of the rational fraction<br />

lim<br />

is obta<strong>in</strong>ed directly.<br />

But if P(a) = Q(a)=0, then it is advisable to camel the b<strong>in</strong>omial * a<br />

P (x)<br />

out of the fraction Q<br />

once or several times.<br />

Example 3.<br />

lim /'T 4 ^ lim xf<br />

!*""!!) f ??<br />

Hm ^^4.

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