# Math Help - solids of revolution/integration question

1. ## solids of revolution/integration question

The volume of the solid formed when the region bounded by the curve $y = e^x - k$ , the x-axis and the line $x=ln3$ is rotated about the x-axis is $pi*ln3$ units cubed. Find k.

2. Originally Posted by shawli
The volume of the solid formed when the region bounded by the curve , the x-axis and the line x=ln3 is rotated about the x-axis is pi*ln3 units cubed. Find k.

is the function $y = e^{x-k}$ or $y = e^x - k$ ?

3. Originally Posted by skeeter

is the function $y = e^{x-k}$ or $y = e^x - k$ ?
The second one, $y = e^x - k$.

4. Originally Posted by shawli
The second one, $y = e^x - k$.
any other information about the constant k ?

5. Nope, that is the question exactly as it is given. I could post the answer at the back of the text book if you'd like to verify your solution though?

6. Originally Posted by shawli
The volume of the solid formed when the region bounded by the curve $y = e^x - k$ , the x-axis and the line $x=ln3$ is rotated about the x-axis is $pi*ln3$ units cubed. Find k.
Solve $\int_{\ln k}^{\ln 3} (e^x - k)^2 \, dx = \ln 3$ for $k$. I get k = 1.