The correct option is C 0.25u6−u5+u4
Using the FOIL rule.
F=First terms, O= Outside terms, I = Inside terms, L= Last terms.
(0.5u3−u2)(0.5u3−u2)
=(12u3−u2)(12u3−u2)
=12u3(12u3−u2)−u2(12u3−u2)
=14u6−12u5−12u5+u4
=14u6−u5+u4
=0.25u6−u5+u4
This is the required expression obtained using FOIL rule.
Also, we can use the identity
(a−b)2=a2−2ab+b2.