How is the value of 4 in 864 related to the value of 4 in 846?

Find the equation using the point (4,8)

Does the point (1, sqrt 7) lie on circle shown.

Estimate the area under the curve f(x) = 16 - x^2 from x = 0 to x = 3 by using three inscribed (under the curve) rectangles. answer to the nearest integer.