1.
∫ ( 10 x 9 + 40 x 4 + 3 ) x 10 + 8 x 5 + 3 x + 5 d x Substitute u = x 10 + 8 x 5 + 3 x + 5 ⟶ d u d x = 10 x 9 + 40 x 4 + 3 ⟶ d x = 1 10 x 9 + 40 x 4 + 3 d u : = ∫ u d u Apply power rule: ∫ u n d u = u n + 1 n + 1 + C with n = 1 2 = 2 u 3 2 3 Substitute back u = x 10 + 8 x 5 + 3 x + 5 : = 2 ( x 10 + 8 x 5 + 3 x + 5 ) 3 2 3 + C Hence, ∫ ( 10 x 9 + 40 x 4 + 3 ) x 10 + 8 x 5 + 3 x + 5 d x = 2 ( x 10 + 8 x 5 + 3 x + 5 ) 3 2 3 + C \int\left(10 x^{9}+40 x^{4}+3\right) \sqrt{x^{10}+8 x^{5}+3 x+5} \mathrm{~d} x\\[4mm]
\text{ Substitute } u=x^{10}+8 x^{5}+3 x+5 \longrightarrow \frac{\mathrm{d} u}{\mathrm{~d} x}=10 x^{9}+40 x^{4}+3 \longrightarrow \mathrm{d} x=\frac{1}{10 x^{9}+40 x^{4}+3} \mathrm{~d} u:\\[4mm]
=\int \sqrt{u} \mathrm{~d} u\\[4mm]
\text{ Apply power rule:}\\[2mm]
\int u^{\mathrm{n}} \mathrm{d} u=\frac{u^{\mathbf{n}+1}}{\mathbf{n}+1} +C\text{ with }\mathbf{n}=\frac{1}{2} =\frac{2 u^{\frac{3}{2}}}{3} \text{ Substitute back } u=x^{10}+8 x^{5}+3 x+5 : \\[3mm] =\frac{2\left(x^{10}+8 x^{5}+3 x+5\right)^{\frac{3}{2}}}{3} +C\\[3mm]
\text{ Hence, }\\[3mm]
\begin{gathered}
\int\left(10 x^{9}+40 x^{4}+3\right) \sqrt{x^{10}+8 x^{5}+3 x+5} d x \\
=\frac{2\left(x^{10}+8 x^{5}+3 x+5\right)^{\frac{3}{2}}}{3}+C
\end{gathered} ∫ ( 10 x 9 + 40 x 4 + 3 ) x 10 + 8 x 5 + 3 x + 5 d x Substitute u = x 10 + 8 x 5 + 3 x + 5 ⟶ d x d u = 10 x 9 + 40 x 4 + 3 ⟶ d x = 10 x 9 + 40 x 4 + 3 1 d u : = ∫ u d u Apply power rule: ∫ u n d u = n + 1 u n + 1 + C with n = 2 1 = 3 2 u 2 3 Substitute back u = x 10 + 8 x 5 + 3 x + 5 : = 3 2 ( x 10 + 8 x 5 + 3 x + 5 ) 2 3 + C Hence, ∫ ( 10 x 9 + 40 x 4 + 3 ) x 10 + 8 x 5 + 3 x + 5 d x = 3 2 ( x 10 + 8 x 5 + 3 x + 5 ) 2 3 + C
2.
∫ 1 ( x − 5 ) ( x 2 + 4 ) d x Perform partial fraction decomposition: = ∫ ( 1 29 ( x − 5 ) − x + 5 29 ( x 2 + 4 ) ) d x Apply linearity: = 1 29 ∫ 1 x − 5 d x − 1 29 ∫ x + 5 x 2 + 4 d x Now solving: ∫ 1 x − 5 d x d u d x = 1 ⟶ d x = d u = ∫ 1 u d u = 1 29 ∫ 1 x − 5 d x − 1 29 ∫ x + 5 x 2 + 4 d x Now solving: ∫ 1 x − 5 d x Substitute u = x − 5 ⟶ d u d x = 1 ⟶ d x = d u : = ∫ 1 u d u This is a standard integral: = ln ( u ) + C Substitute back u = x − 5 = ln ( x − 5 ) + C Now solving: ∫ x + 5 x 2 + 4 d x Expand: = ∫ ( x x 2 + 4 + 5 x 2 + 4 ) d x = ∫ x x 2 + 4 d x + 5 ∫ 1 x 2 + 4 d x \int \frac{1}{(x-5)\left(x^{2}+4\right)} d x\\[4mm]
\text{ Perform partial fraction decomposition:}\\[2mm]
=\int\left(\frac{1}{29(x-5)}-\frac{x+5}{29\left(x^{2}+4\right)}\right) d x\\[2mm]
\text{ Apply linearity: } \\=\frac{1}{29} \int \frac{1}{x-5} \mathrm{~d} x-\frac{1}{29} \int \frac{x+5}{x^{2}+4} \mathrm{~d} x \\
\text{Now solving: }\\
\int \frac{1}{x-5} \mathrm{~d} x \\[4mm]
\frac{\mathrm{d} u}{\mathrm{~d} x}=1 \longrightarrow \mathrm{d} x=\mathrm{d} u =\int \frac{1}{u} \mathrm{~d} u\\[2mm]
\begin{gathered}
=\frac{1}{29} \int \frac{1}{x-5} \mathrm{~d} x-\frac{1}{29} \int \frac{x+5}{x^{2}+4} \mathrm{~d} x \\[3mm]
\text { Now solving: } \\[2mm]
\int \frac{1}{x-5} \mathrm{~d} x \\
\text { Substitute } u=x-5 \longrightarrow \frac{\mathrm{d} u}{\mathrm{~d} x}=1 \longrightarrow \mathrm{d} x=\mathrm{d} u:
\end{gathered}\\[2mm]
=\int \frac{1}{u} \mathrm{~d} u\\[3mm]
\text{ This is a standard integral:}\\[2mm]
=\ln (u)+C\\[3mm]
\text{ Substitute back} \,u = x-5\\
=\ln (x-5)+C\\[3mm]
\text{ Now solving:}\\[2mm]
\int \frac{x+5}{x^{2}+4} d x\\[3mm]
\text{ Expand:}\\[2mm]
=\int\left(\frac{x}{x^{2}+4}+\frac{5}{x^{2}+4}\right) d x\\
=\int \frac{x}{x^{2}+4} \mathrm{~d} x+5 \int \frac{1}{x^{2}+4} \mathrm{~d} x ∫ ( x − 5 ) ( x 2 + 4 ) 1 d x Perform partial fraction decomposition: = ∫ ( 29 ( x − 5 ) 1 − 29 ( x 2 + 4 ) x + 5 ) d x Apply linearity: = 29 1 ∫ x − 5 1 d x − 29 1 ∫ x 2 + 4 x + 5 d x Now solving: ∫ x − 5 1 d x d x d u = 1 ⟶ d x = d u = ∫ u 1 d u = 29 1 ∫ x − 5 1 d x − 29 1 ∫ x 2 + 4 x + 5 d x Now solving: ∫ x − 5 1 d x Substitute u = x − 5 ⟶ d x d u = 1 ⟶ d x = d u : = ∫ u 1 d u This is a standard integral: = ln ( u ) + C Substitute back u = x − 5 = ln ( x − 5 ) + C Now solving: ∫ x 2 + 4 x + 5 d x Expand: = ∫ ( x 2 + 4 x + x 2 + 4 5 ) d x = ∫ x 2 + 4 x d x + 5 ∫ x 2 + 4 1 d x
Now solving: ∫ x x 2 + 4 d x Substitute u = x 2 + 4 ⟶ d u d x = 2 x ⟶ d x = 1 2 x d u : = 1 2 ∫ 1 u d u Now solving: ∫ 1 u d u Use previous result: = ln ( u ) + C 1 Plug in solved integrals: 1 2 ∫ 1 u d u = ln ( u ) 2 + C Substitute back u = x 2 + 4 : = ln ( x 2 + 4 ) 2 + C Now solving: ∫ 1 x 2 + 4 d x Substitute u = x 2 ⟶ d u d x = 1 2 ⟶ d x = 2 d u : = ∫ 2 4 u 2 + 4 d u \text{ Now solving:}\\[2mm]
\int \frac{x}{x^{2}+4} d x\\[3mm]
\text{ Substitute } u=x^{2}+4 \longrightarrow \frac{\mathrm{d} u}{\mathrm{~d} x}=2 x \longrightarrow \mathrm{d} x=\frac{1}{2 x} \mathrm{~d} u :\\[2mm]
=\frac{1}{2} \int \frac{1}{u} \mathrm{~d} u\\[3mm]
\text{ Now solving:}\\[2mm]
\int \frac{1}{u} \mathrm{~d} u\\[2mm]
\text{ Use previous result:}\\[2mm]
=\ln (u)+C_1\\[2mm]
\text{ Plug in solved integrals:}\\[2mm]
\begin{aligned}
&\frac{1}{2} \int \frac{1}{u} \mathrm{~d} u \\
&=\frac{\ln (u)}{2}+C
\end{aligned}
\\[2mm]
\text{Substitute back } u=x^{2}+4 :\\[2mm]
=\frac{\ln \left(x^{2}+4\right)}{2}+C\\[3mm]
\text{ Now solving:}\\[2mm]
\int \frac{1}{x^{2}+4} \mathrm{~d} x\\[2mm]
\text{ Substitute } u=\frac{x}{2} \longrightarrow \frac{\mathrm{d} u}{\mathrm{~d} x}=\frac{1}{2} \longrightarrow \mathrm{d} x=2 \mathrm{~d} u :\\[2mm]
=\int \frac{2}{4 u^{2}+4} d u Now solving: ∫ x 2 + 4 x d x Substitute u = x 2 + 4 ⟶ d x d u = 2 x ⟶ d x = 2 x 1 d u : = 2 1 ∫ u 1 d u Now solving: ∫ u 1 d u Use previous result: = ln ( u ) + C 1 Plug in solved integrals: 2 1 ∫ u 1 d u = 2 ln ( u ) + C Substitute back u = x 2 + 4 : = 2 ln ( x 2 + 4 ) + C Now solving: ∫ x 2 + 4 1 d x Substitute u = 2 x ⟶ d x d u = 2 1 ⟶ d x = 2 d u : = ∫ 4 u 2 + 4 2 d u
Simplify: = 1 2 ∫ 1 u 2 + 1 d u Now solving: ∫ 1 u 2 + 1 d u This is a standard integral: = arctan ( u ) + C 1 Plug in solved integrals: 1 2 ∫ 1 u 2 + 1 d u = arctan ( u ) 2 + C Substitute back u = x 2 : = arctan ( x 2 ) 2 + C Plug in solved integrals: ∫ x x 2 + 4 d x + 5 ∫ 1 x 2 + 4 d x = ln ( x 2 + 4 ) 2 + 5 arctan ( x 2 ) 2 + C Plug in solved integrals: 1 29 ∫ 1 x − 5 d x − 1 29 ∫ x + 5 x 2 + 4 d x = − ln ( x 2 + 4 ) 58 − 5 arctan ( x 2 ) 58 + ln ( x − 5 ) 29 + C \text{ Simplify: }\\[2mm]
=\frac{1}{2} \int \frac{1}{u^{2}+1} \mathrm{~d} u\\[2mm]
\text{ Now solving:}\\[2mm]
\int \frac{1}{u^{2}+1} d u\\[2mm]
\text{ This is a standard integral:}
=\arctan (u)+C_1\\[2mm]
\text{ Plug in solved integrals:}\\[2mm]
\begin{gathered}
\frac{1}{2} \int \frac{1}{u^{2}+1} \mathrm{~d} u \\
=\frac{\arctan (u)}{2} +C\\
\text { Substitute back } u=\frac{x}{2} \text { : } \\
=\frac{\arctan \left(\frac{x}{2}\right)}{2}+C
\end{gathered}
\\[2mm]
\text{ Plug in solved integrals:}\\
\begin{aligned}
&\int \frac{x}{x^{2}+4} \mathrm{~d} x+5 \int \frac{1}{x^{2}+4} \mathrm{~d} x \\
&=\frac{\ln \left(x^{2}+4\right)}{2}+\frac{5 \arctan \left(\frac{x}{2}\right)}{2}+C
\end{aligned}\\[2mm]
\text{ Plug in solved integrals:}\\[2mm]
\begin{gathered}
\frac{1}{29} \int \frac{1}{x-5} \mathrm{~d} x-\frac{1}{29} \int \frac{x+5}{x^{2}+4} \mathrm{~d} x \\
=-\frac{\ln \left(x^{2}+4\right)}{58}-\frac{5 \arctan \left(\frac{x}{2}\right)}{58}+\frac{\ln (x-5)}{29}+C
\end{gathered} Simplify: = 2 1 ∫ u 2 + 1 1 d u Now solving: ∫ u 2 + 1 1 d u This is a standard integral: = arctan ( u ) + C 1 Plug in solved integrals: 2 1 ∫ u 2 + 1 1 d u = 2 arctan ( u ) + C Substitute back u = 2 x : = 2 arctan ( 2 x ) + C Plug in solved integrals: ∫ x 2 + 4 x d x + 5 ∫ x 2 + 4 1 d x = 2 ln ( x 2 + 4 ) + 2 5 arctan ( 2 x ) + C Plug in solved integrals: 29 1 ∫ x − 5 1 d x − 29 1 ∫ x 2 + 4 x + 5 d x = − 58 ln ( x 2 + 4 ) − 58 5 arctan ( 2 x ) + 29 ln ( x − 5 ) + C
The problem is solved. Apply the absolute value function to arguments of logarithm functions in order to extend the antiderivative’s domain: ∫ 1 ( x − 5 ) ( x 2 + 4 ) d x = − ln ( x 2 + 4 ) 58 − 5 arctan ( x 2 ) 58 + ln ( ∣ x − 5 ∣ ) 29 + C = − ln ( x 2 + 4 ) + 5 arctan ( x 2 ) − 2 ln ( ∣ x − 5 ∣ ) 58 + C \text{The problem is solved. Apply the absolute value function to arguments of}\\ \text{logarithm functions in order to extend the antiderivative's domain:}\\[2mm]
\begin{aligned}
& \int \frac{1}{(x-5)\left(x^{2}+4\right)} d x \\
=-& \frac{\ln \left(x^{2}+4\right)}{58}-\frac{5 \arctan \left(\frac{x}{2}\right)}{58}+\frac{\ln (|x-5|)}{29}+C \\
=&-\frac{\ln \left(x^{2}+4\right)+5 \arctan \left(\frac{x}{2}\right)-2 \ln (|x-5|)}{58}+C
\end{aligned} The problem is solved. Apply the absolute value function to arguments of logarithm functions in order to extend the antiderivative’s domain: = − = ∫ ( x − 5 ) ( x 2 + 4 ) 1 d x 58 ln ( x 2 + 4 ) − 58 5 arctan ( 2 x ) + 29 ln ( ∣ x − 5∣ ) + C − 58 ln ( x 2 + 4 ) + 5 arctan ( 2 x ) − 2 ln ( ∣ x − 5∣ ) + C
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