if c2+ d2= 4 and (c-d)2 = 2, what is the value of cd?

if c²+ d²= 4 and (c-d)² = 2, what is the value of cd?

A 1

B √2

C 2

D 3

Correct Answer: Option A

here, c2+ d2= 4 and (c-d)2 = 2 so, (c-d)2 =c2+ d2-2cd or,2cd = (c2+d2)-(c-d)2 or2cd=4-2 or,2cd=2 so, cd=1