Question

The maximum value of the function f(x, y, z)=x²+y²+z², where Ix+my+nz =p is​

Answer 1

If x²+y²=4, what is the maximum value of x+y?

This is an example of a seemingly very hard question that has a very simple answer.

If x^2 + y^2 = 4…then you’re on a circle of radius 2 centered at the origin.

If x + y = M, then you’re on a straight line passing between the points (0, M) and (M, 0).