Answer:
C
Step-by-step explanation:
We want to integrate:
[tex]\displaystyle \int\frac{4x^4+3}{4x^5+15x+2}\,dx[/tex]
Notice that the expression in the denominator is quite similar to the expression in the numerator. So, we can try performing u-substitution. Let u be the function in the denominator. So:
[tex]u=4x^5+15x+2[/tex]
By differentiating both sides with respect to x:
[tex]\displaystyle \frac{du}{dx}=20x^4+15[/tex]
We can "multiply" both sides by dx:
[tex]du=20x^4+15\,dx[/tex]
And divide both sides by 5:
[tex]\displaystyle \frac{1}{5}\, du=4x^4+3\,dx[/tex]
Rewriting our original integral yields:
[tex]\displaystyle \int \frac{1}{4x^5+15x+2}(4x^4+3\, dx)[/tex]
Substitute:
[tex]\displaystyle =\int \frac{1}{u}\Big(\frac{1}{5} \, du\Big)[/tex]
Simplify:
[tex]\displaystyle =\frac{1}{5}\int \frac{1}{u}\, du[/tex]
This is a common integral:
[tex]\displaystyle =\frac{1}{5}\ln|u|[/tex]
Back-substitute. Of course, we need the constant of integration:
[tex]\displaystyle =\frac{1}{5}\ln|4x^5+15x+2|+C[/tex]
Our answer is C.
