7√41

x^2 - y^2 = (x+y)(x-y) x+y=7 x-y=SQRT((x+y)^2 - 4xy) x-y=SQRT(41)

hence x^2 - y^2 = 7√41

If x, y, z are 3 non zero positive integers such that x+y+z = 8 and xy+yz+zx = 20, then What would be minimum possible value of x*y^2*z^2

If x + y = 7 & x^3 + y^3 = 133 Then xy=??

Where x,y both are real numbers.

The temperature on a unit sphere x^2 + y^2 + z^2 = 1, is given by a temperature distribution

T(x,y,z) = 50.(xy + yz)

What is the temperature difference between the coldest and warmest point on the sphere?