A torus is formed when a circle of radius 2 centered at \( (4,0) \) is revolved about the \( y \)-axis. a. Use the shell method to write an integral for the volume of the torus. b. Use the washer method to write an integral for the volume of the torus. c. Find the volume of the torus by evaluating one of the two integrals obtained in parts (a) and (b). (Hint: Both integrals can be evaluated without using the Fundamental Theorem of Calculus.)

nction définie par \( f(x)=\frac{L}{x^{2}+1} \)

Determine the indefinite integral \( \int (6x^3 + 4x^2) \, dx \)

If the slope of the tangent to the curve: \( y=f(x) \) at any point on it equals \( 6 x+a \), whe \( a \) is constant if the equation of the tangent to the curve at the point \( (1,-1) \) is \( y=4- \) \( 5 x \), then the equation of the curve is ... \( \begin{array}{llll}\text { a) } y=3 x^{2}-4 & \text { b) } y=3 x^{2}-11 x+7 & \text { c) } y=3 x^{2}-4 x & \text { d) } y=3 x^{2}-x-3\end{array} \)

3. \( \lim _{x \rightarrow \infty} \frac{x-1}{2 x+5} \)

Show that \( \Gamma\left(\frac{1}{2}\right)=\sqrt{\pi} \)