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límits i continuïtat de funcions - matessantboianes

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⎛ 2 2<br />

x<br />

x<br />

a) lim<br />

⎜ − 1 1+ 2 ⎞<br />

⎜ − → ` − `<br />

x→<br />

+ `⎝⎜<br />

x 2x−1 ⎠⎟<br />

x ` x `<br />

x→<br />

+ `<br />

2<br />

−x −3x<br />

+ 1 1<br />

=−<br />

2 2 x − x 2<br />

Solucionari<br />

⎛ x − + x ⎞<br />

lim<br />

⎜ − lim<br />

→+ ⎝⎜<br />

x x − ⎠⎟<br />

→+<br />

=<br />

2 2<br />

2 2<br />

1 1 2<br />

( x −1)( 2x −1) − ( 1+ 2 x ) x<br />

=<br />

2 1<br />

x( 2x − 1)<br />

b) lim<br />

x→<br />

+ `<br />

=<br />

lim ( 2 x −2x − x )= lim<br />

x→+ `<br />

x→+<br />

`<br />

c) lim<br />

x→<br />

+ `<br />

lim<br />

( 2 x −2x − x ) → ` − `<br />

=<br />

lim<br />

x→<br />

+ `<br />

( 2x − 1+ 4 x ) → ` − `<br />

lim ( 2x − 1+ 4 x )= lim<br />

x→+ `<br />

x→<br />

+ `<br />

d) lim<br />

x→<br />

+ `<br />

lim<br />

x→<br />

+ `<br />

( 2 9x + 3x −3x)<br />

→ ` − `<br />

( 9x + 3x −3x)=<br />

2 lim<br />

x→<br />

+ `<br />

=<br />

lim<br />

x→<br />

+ `<br />

2 2<br />

x −2x − x<br />

=<br />

2 x − 2 x + x<br />

−2<br />

x<br />

=−1<br />

2 x − 2 x + x<br />

2<br />

4 x −1−4x 2x + 1+ 4 x<br />

020 Substitueix a, b, c i d per nombres <strong>de</strong> manera que:<br />

a) lim<br />

x → + `<br />

b) lim<br />

x → + `<br />

( x + ax − x )=<br />

2 1<br />

( 2 4 x + bx−3 − 2 x )=−<br />

1<br />

4<br />

( ) =<br />

=+ `<br />

2 2<br />

9x + 3x −9x<br />

=<br />

2 9x + 3x + 3 x<br />

3 x<br />

1<br />

=<br />

2 9x+ 3x<br />

+ 3 x 2<br />

c) lim<br />

x → + `<br />

d) lim<br />

x → + `<br />

2 2<br />

( 2 9x + 7 −cx)=<br />

0<br />

7<br />

( dx + x− − x )=+<br />

2 5 2 `<br />

a) lim 2 x + ax − x lim<br />

x + ax − x<br />

= lim<br />

ax<br />

=<br />

x→+ ` x→+<br />

` 2 x + ax + x x→<br />

+ ` 2 x + ax + x<br />

=<br />

a<br />

2<br />

= 1→a= 2<br />

b) lim ( 2 4 x + bx −3 − 2 x)=<br />

lim<br />

x→+ ` x→+<br />

`<br />

=<br />

lim<br />

x→<br />

+ `<br />

2 2<br />

4 x + bx −3−4x =<br />

2 4 x + bx − 3 + 2x<br />

bx − 3<br />

b 1<br />

= =−→<br />

b =−1<br />

2 4 x + bx − 3 + 2 x 4 4<br />

419

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