i). $ \int k dx = kx + c \, $ dimana k yaitu sebuah konstanta
ii). $ \int k f(x) dx = k \int f(x) dx $
iii). $ \int [f(x) + g(x) ] dx = \int f(x) dx + \int g(x) dx $
iv). $ \int [f(x) - g(x) ] dx = \int f(x) dx - \int g(x) dx $
Lalu pada bab mana ini akan mempermudah penyelesaian soal soal integral? Anda perhatikan pola soal penerapan sifat sifat integral di bawah ini,
Soal 1. $ \int 3 dx $
$ \int 3 dx = 3x + c \, $ (sifat i)
Soal 2. $ \int (x^2 + x) dx $
menurut sifat (iii) :
$ \int (x^2 + x) dx = \int x^2 dx + \int x dx = \frac{1}{2+1}x^{2+1} + \frac{1}{1+1}x^{1+1} + c = \frac{1}{3}x^3 + \frac{1}{2}x^2 + c $
Soal 3. $ \int (x^3 - 2x + 5) dx $
$ \begin{align} \int (x^3 - 2x + 5) dx & = \int x^3 dx - \int 2x dx + \int 5 dx \\ & = \frac{1}{3+1}x^{3+1} - \frac{2}{1+1}x^{1+1} + 5x + c \\ & = \frac{1}{4}x^4 - \frac{2}{2}x^2 + 5 + c \\ & = \frac{1}{4}x^4 - \frac{2}{2}x^2 + 5 + c \\ & = \frac{1}{4}x^4 - x^2 + 5 + c \end{align} $
Soal 4. $ \int \frac{x^3+2x^2-1}{3x^2} dx $
Sifat Perpangkatan : $ \frac{1}{a^n} = a^{-n} , \, \frac{a^m}{a^n} = a^{m-n} $ .
$ \begin{align} \int \frac{x^3+2x^2-1}{3x^2} dx & = \int \frac{x^3}{3x^2}+\frac{2x^2}{3x^2}-\frac{1}{3x^2} dx \\ & = \int \frac{x}{3 }+\frac{2 }{3 }-\frac{1}{3x^2} dx \\ & = \int \frac{1}{3}x +\frac{2 }{3 }-\frac{1}{3 } x^{-2} dx \\ & = \frac{1}{3}. \frac{1}{1+1}x^{1+1} +\frac{2 }{3 }x-\frac{1}{3 }. \frac{1}{-2+1} x^{-2+1} + c \\ & = \frac{1}{3}. \frac{1}{2}x^2 +\frac{2 }{3 }x-\frac{1}{3 }. \frac{1}{- 1} x^{- 1} + c \\ & = \frac{1}{6}x^2 +\frac{2 }{3 }x + \frac{1}{3 } . \frac{1}{x} + c \\ & = \frac{1}{6}x^2 +\frac{2 }{3 }x + \frac{1}{3 x} + c \end{align} $ Sumber http://www.marthamatika.com/
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