integrate the problem

integral(4x/sqrt(8x^2-1), dx, 2, 1)

2. What does the problem say? I do not want to download and open that document for security reasons

3. Let u=8x^2+1, du=16x

4. Originally Posted by taichi2910
integrate the problem

integral(4x/sqrt(8x^2-1), dx, 2, 1)
$\int^{2}_{1} \frac{4x}{\sqrt{8x^2-1}} dx$

$4 \int^{2}_{1} \frac{x}{\sqrt{8x^2-1}} dx$

Do a substitution with:

$u = 8x^2-1$

$du = 16x dx$

*Change your limits by plugging in your original limits into the equation for u

$\frac{1}{4} \int^{31}_{7} \frac{1}{u} du$

$= [\frac{\sqrt{u}}{2}]^{31}_{7}$

Then evaluate!