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2
2. Tentukan turunan dari f(x) = 3x
Penyelesaian
2
f(x) = 3x
f(x + h) = 3(x + h) 2
2 2
= 3(x + 2xh + h )
2
2
= 3x + 6xh + 3h
f x ( + h) − f ( x)
maka: f (' x) = lim
h→ 0 h
2
+
x 3 ( 2 + 6 xh 3 h ) − x 3 2
= lim
h→ 0 h
6 xh + h 3 2
= lim
h→ 0 h
= lim 6 +x 3h
h → 0

= 6x+ 3.0
= 6x
Latihan

Dengan definisi di atas tentukan nilai turunan berikut:
1. f(x) = 6 – 2 x ⇒ f ( ' x ) = − 2

2
2. f(x) = 5x +2x⇒ f ( ' x ) = 10 + 2
x
1 − 2
3. f (x ) = ⇒ ( ' f ) x =
x 2 x 3

4. f ( x = x ⇒ f (' x) = 1
)
2 x