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MATEMATIKA 1 skripta studij: Biotehnologija i Prehrambena ... - PBF

MATEMATIKA 1 skripta studij: Biotehnologija i Prehrambena ... - PBF

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= 4 lim<br />

x→+∞<br />

b)<br />

= 4 lim<br />

x→−∞<br />

x √<br />

x 2<br />

√<br />

x 2 +2x+3+ √ x 2 −2x+3 √<br />

x 2<br />

lim f(x) = lim<br />

x→−∞ x→−∞<br />

x √<br />

x 2<br />

√<br />

x 2 +2x+3+ √ x 2 −2x+3 √<br />

x 2<br />

= 4 lim<br />

x→+∞<br />

1<br />

√<br />

1+ 2 + 3 +<br />

x x 2<br />

√<br />

1− 2 x + 3<br />

x 2 = 4 2 = 2.<br />

∣ 4x ∣∣∣<br />

√<br />

x2 +2x+3+ √ x 2 −2x+3 = −∞<br />

∞ ∣<br />

= 4 lim<br />

x→−∞<br />

−1<br />

√<br />

1+ 2 + 3 +<br />

x x 2<br />

√<br />

1− 2 x + 3<br />

x 2 = −4<br />

2 = −2.<br />

Zadatak 72 Izračunajte a) lim x→+∞ ( 3√ x 3 +3x 2 −x)<br />

b) lim x→+∞ ( √ x 2 −2x−x) c) lim x→+∞ ( 3√ x 3 +3x 2 − √ x 2 −2x).<br />

Rješenje: a)<br />

√<br />

lim ( 3√ x 3 +3x 2 −x) = |∞−∞| = lim ( 3√ 3 (x3 +3x<br />

x 3 +3x 2 −x)<br />

2 ) 2 +x 3√ x 3 +3x 2 +x 2<br />

√<br />

x→+∞ x→+∞ 3 (x3 +3x 2 ) 2 +x 3√ x 3 +3x 2 +x 2<br />

= lim<br />

x→+∞<br />

= lim<br />

x→+∞<br />

3x 2 ∣ ∣∣<br />

√<br />

3 (x3 +3x 2 ) 2 +x 3√ x 3 +3x 2 +x = ∞<br />

∣<br />

2 ∞<br />

3x 2 | : x 2<br />

√<br />

(x3 +3x 2 ) 2 +x 3√ x 3 +3x 2 +x 2 | : x = 3 lim 2<br />

3<br />

x→+∞<br />

1<br />

= 1.<br />

√(1+ 3 x )2 +<br />

√1+ 3 3 +1 x<br />

b)<br />

√<br />

lim (√ x 2 −2x−x) = |∞−∞| = lim (√ x2 −2x+x<br />

x 2 −2x−x) √<br />

x→+∞ x→+∞ x2 −2x+x<br />

∣ −2x ∣∣∣<br />

= lim √<br />

x→∞ x2 −2x+x = −∞<br />

x 1<br />

∞ ∣ = −2 lim √ = −2 lim = −1.<br />

x→∞ x2 −2x+x x→∞<br />

√1− 2 +1 x<br />

c)<br />

lim<br />

x→+∞ ( 3√ x 3 +3x 2 − √ x 2 −2x) = |∞−∞| = lim<br />

x→+∞ ( 3√ x 3 +3x 2 −x−( √ x 2 −2x−x))<br />

= lim<br />

x→+∞ ( 3√ x 3 +3x 2 −x)− lim<br />

x→∞<br />

( √ x 2 −2x−x) = 1−(−1) = 2.<br />

3<br />

61

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