Saying that 4 < sqrt(x) < 9 is equivalent to is saying what about x?

7. if the value of x varies directly with the value of y, and x = 3 when y = 21. what is the valu y, and x = 3 when y = 21. what is the value of x when y = 105?

Use the method of cylindrical shells to find the volume v generated by rotating the region bounded by the curves about the given axis.y = 7ex, y = 7e^-x, x = 1; about the y-axis

The length of a rectangle plus its width is 24 cm. the area is 143 square cm. what are the length and width of the rectangle?