Latihan Matematika Wajib Kelas XI Integral Substitusi
# 2
Pilgan

Hasil dari adalah ....

A

B

C

D

E

Pembahasan:

Misalkan u=6x24u=6x^2-4 , maka du=12x dxdu=12x\ dx dx=du12x\Leftrightarrow dx=\frac{du}{12x}

Sehingga menjadi:

πx6x24dx=π16x24x dx\int\frac{\pi x}{\sqrt{6x^2-4}}dx=\pi\int\frac{1}{\sqrt{6x^2-4}}x\ dx

=π1ux du12x=\pi\int\frac{1}{\sqrt{u}}x\ \frac{du}{12x}

=π1udu12=\pi\int\frac{1}{\sqrt{u}}\frac{du}{12}, ingat bahwa x=x12 \sqrt{x}=x^{\frac{1}{2\ }} dan 1xn=xn\frac{1}{x^n}=x^{-n}

=π12u12du=\frac{\pi}{12}\int u^{-\frac{1}{2}}du, untuk f(x)=axn, n1f\left(x\right)=ax^n,\ n\ne-1 maka axndx=an+1xn+1+C\int ax^ndx=\frac{a}{n+1}x^{n+1}+C

=π12(112+1u12+1)+C=\frac{\pi}{12}\left(\frac{1}{-\frac{1}{2}+1}u^{-\frac{1}{2}+1}\right)+C

=π12(112+22u12+22)+C=\frac{\pi}{12}\left(\frac{1}{-\frac{1}{2}+\frac{2}{2}}u^{-\frac{1}{2}+\frac{2}{2}}\right)+C

=π12(112u12)+C=\frac{\pi}{12}\left(\frac{1}{\frac{1}{2}}u^{\frac{1}{2}}\right)+C

=π12(2u)+C=\frac{\pi}{12}\left(2\sqrt{u}\right)+C

=π6u+C=\frac{\pi}{6}\sqrt{u}+C

=π66x24+C=\frac{\pi}{6}\sqrt{6x^2-4}+C


Jadi, hasil integral substitusi tersebut adalah π66x24+C\frac{\pi}{6}\sqrt{6x^2-4}+C