Latihan Matematika Wajib Kelas XI Integral Substitusi
# 3
Pilgan

Hasil dari adalah ....

A

B

C

D

E

Pembahasan:

Misalkan u=5x22u=5x^2-2, maka du=10xdxdu=10x dx dx=du10x\Leftrightarrow dx=\frac{du}{10x}

Sehingga menjadi:

x5x22dx=(5x22)12x dx\int x\sqrt{5x^2-2}dx=\int\left(5x^2-2\right)^{\frac{1}{2}}x\ dx

=u12x du10x=\int u^{\frac{1}{2}}x\ \frac{du}{10x}

=u12du10=\int u^{\frac{1}{2}}\frac{du}{10}

=110u12du=\frac{1}{10}\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

=110(112+1u12+1)+C=\frac{1}{10}\left(\frac{1}{\frac{1}{2}+1}u^{\frac{1}{2}+1}\right)+C

=110(112+22u12+22)+C=\frac{1}{10}\left(\frac{1}{\frac{1}{2}+\frac{2}{2}}u^{\frac{1}{2}+\frac{2}{2}}\right)+C

=110(132u32)+C=\frac{1}{10}\left(\frac{1}{\frac{3}{2}}u^{\frac{3}{2}}\right)+C

=110(23u32)+C=\frac{1}{10}\left(\frac{2}{3}u^{\frac{3}{2}}\right)+C

=115(u22)(u12)+C=\frac{1}{15}\left(u^{\frac{2}{2}}\right)\left(u^{\frac{1}{2}}\right)+C

=115uu+C=\frac{1}{15}u\sqrt{u}+C

=115(5x22)5x22+C=\frac{1}{15}\left(5x^2-2\right)\sqrt{5x^2-2}+C


Jadi, hasil integral substitusi tersebut adalah 115(5x22)5x22+C\frac{1}{15}\left(5x^2-2\right)\sqrt{5x^2-2}+C