定積分例題訓練

Preparing發表於2024-05-05

exercise 1

\[\begin{eqnarray} \int \frac{1}{\sqrt[]{x}}dx \newline \newline \int \frac{1}{\sqrt[]{x}}dx=\int \frac{1}{x^{\frac{1}{2}}}dx=\int x^{-\frac{1}{2}}dx \newline \newline \Rightarrow \frac{1}{-\frac{1}{2}+1}x^{-\frac{1}{2}+1}+C \newline \newline 2 \times x^{\frac{1}{2}}+C \newline \newline 2\sqrt[]{x} +C \end{eqnarray} \]


exercise 2

\[ \begin{align} \int x^{2} \times \sqrt[3]{x} dx \\ \\ \because x^{2} \times \sqrt[3]{x} \Rightarrow x^{2+\frac{1}{3} }=x^{\frac{7}{3} } \\ \\ \therefore \int x^{\frac{7}{3} }dx= \frac{1}{\frac{7}{3}+1} x^{\frac{7}{3} +1 } + C \\ \\ \Rightarrow \frac{3}{10} x^{\frac{10}{3} } + C \end{align} \]

exercise 3

\[\begin{align} \int(\sqrt{x}+1)(x-\sqrt{x}) d x=? \\ \\ \Rightarrow \int\left(x^{\frac{1}{2}}+1\right)\left(x-x^{-\frac{1}{2}}\right) d x \\ \\ = \int(x^{\frac{3}{2}}-1+x-x^{-\frac{1}{2}} )dx \\ \\ \int x^{\frac{3}{2}} d x=\frac{1}{\frac{3}{2}+1} x^{\frac{3}{2}+1}=\frac{2}{5} x^{\frac{5}{2}} \\ \\ \int x d x=\frac{1}{1+1} x^{1+1}=\frac{1}{2} x^{2} \\ \\ \int x^{-\frac{1}{2}} d x=\frac{1}{-\frac{1}{2}+1} x^{-\frac{1}{2}+1}=2 x^{\frac{1}{2}} \\ \\ \int 1 d x=x \\ \\ \Rightarrow \frac{2}{5} x^{\frac{5}{2}}-x+\frac{1}{2} x^{2}-2 x^{\frac{1}{2}}+C \end{align} \]

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