a. f(x,y)=12xy(x2+y2) f(x, y) = \frac12xy\big(x^2+y^2\big)\;\;f(x,y)=21xy(x2+y2) b. V=∫01∫01f(x,y)dxdy=18 V = \int_0^1\int_0^1f(x, y)dxdy =\frac18\;\;V=∫01∫01f(x,y)dxdy=81 c. fprom=18f_{prom} =\frac18fprom=81 d.
