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Contoh 7.6.2<br />

Hitunglah limit yang diberikan:<br />

a. lim<br />

x →−∞<br />

x + 5<br />

2<br />

2x−3 b. lim ( x →+∞<br />

2<br />

x + 2x<br />

−<br />

2<br />

x − x)<br />

Penyelesaian:<br />

a. Pangkat tertinggi dari x adalah 2 yang muncul di bawah tanda akar. Karena itu<br />

pembilang dan penyebut kita bagi dengan<br />

dan x =− x . Jadi,<br />

lim<br />

x →−∞<br />

x + 5<br />

2<br />

2x−3 =<br />

lim<br />

x →−∞<br />

x 5<br />

+<br />

x x<br />

3<br />

2 − 2<br />

x<br />

b. Kita rasionalkan bentuk akar itu,<br />

2 2<br />

( x + x − x − x)<br />

lim 2<br />

x →+∞<br />

2<br />

x = x . Karena x →−∞, maka x < 0<br />

BAB VII ~ Limit Fungsi 253<br />

=<br />

=<br />

=<br />

lim<br />

x →−∞<br />

lim<br />

x →−∞<br />

−1−0 2− 0<br />

=<br />

2 2<br />

= lim ( x 2x<br />

x x)<br />

=<br />

=<br />

=<br />

x →+∞<br />

lim<br />

x →+∞<br />

lim<br />

x →+∞<br />

lim<br />

x →+∞<br />

+ − − ⋅<br />

2 2<br />

x + 2x<br />

− x + x<br />

2 2<br />

x + 2x<br />

+ x −x<br />

x<br />

3x<br />

2<br />

1+ + x<br />

x<br />

1<br />

1−<br />

x<br />

x 5<br />

+<br />

−x−x 3<br />

2 − 2<br />

x<br />

5<br />

−1− x<br />

3<br />

2 − 2<br />

x<br />

3<br />

2<br />

1+ +<br />

x<br />

1<br />

1−<br />

x<br />

=<br />

−1<br />

2<br />

2 2<br />

x + 2x<br />

+ x − x<br />

2 2<br />

x + 2x<br />

+ x − x<br />

3<br />

1+ 0 + 1− 0<br />

= 3<br />

2<br />

W

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