What is the x-value of the vertex of f(x) = -x2 + 9x - 11 ?

Determine whether the following statements are true and give an explanation or counterexample. bold a. when using the shell method, the axis of the cylindrical shells is parallel to the axis of revolution. bold b. if a region is revolved about the y-axis, then the shell method must be used. bold c. if a region is revolved about the x-axis, then in principle it is possible to use the disk/washer method and integrate with respect to x or the shell method and integrate with respect to y.

How to choose the sign of the radical in the denominator of the formula for the distance from a point to a line.

Through non-collinear points there is exactly one plane.