# Math Help - area between curve and x-axis

1. ## area between curve and x-axis

Find the area bounded by the following:

$
y=\frac{1}{\sqrt{3x+7}} ; x=-1, x=3,x-axis
$

2. Originally Posted by Punch
Find the area bounded by the following:

$
y=\frac{1}{\sqrt{3x+7}} ; x=-1, x=3,x-axis
$
$\int_{-1}^{3}\frac{dx}{\sqrt{3x+7}}\,\, ;u=3x+7 \implies du=3dx \implies \frac{1}{4}\int_{4}^{16}u^{-\frac{1}{2}}du$

3. ## Correct me if I am wrong

Originally Posted by Punch
Find the area bounded by the following:

$
y=\frac{1}{\sqrt{3x+7}} ; x=-1, x=3,x-axis
$
Correct me if I am wrong, but I believe the multiplier outside of the integral should be one third

4. sorry emptyset.. but i dont understand the part where u wrote $\int_{4}^{16}u^{-\frac{1}{2}}du$

isnt it suppose to be 3 on top and -1 below?

5. Those are the limits for x, but you are now working with the variable u = 3x+7.

Check out what the values of u are when x=-1 and x=3.