Evaluate: a+ib−c+idc+ida−ib.Answer: a2+b2+c2+d2SolutionExpand along the leading diagonal minus the off diagonal.=(a+ib)(a−ib)−(c+id)(−c+id)=(a2−i2b2)−(i2d2−c2).Since i2=−1,=(a2+b2)−(−d2−c2)=a2+b2+c2+d2.a2+b2+c2+d2CBSE Class 12 Board · 2008 · Subjective