CBSE Class 12 Math 2008 Solved Paper

Question : 4 of 29

Marks: +1, -0

Evaluate:

|\table a+ib,c+id;-c+id,a-ib|

Solution:

|\table a+ib,c+id;-c+id,a-ib|

= (a + ib) (a – ib) – (c + id) (-c + id)
=

(a^2 – i^2b^2)

–

(-c^2 + i^2d^2)

(a^2 + b^2)

–

(-c^2 – d^2)

(∵

i^2

= -1)
=

a^2 + b^2 + c^2 + d^2

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