1.

If z = (2+ 3i) ( 1+ 2i) find z-¹

Answer»

Z = (2 + 3i)(1 + 2i)

= 2 + 4i + 3i + 6i2

= 2 – 6 + 7i    \((\because i^2 =-1)\)

= –4 + 7i

Now, Z–1 \(=\frac{1}{z}=\frac{1}{-4+7i}\)

\(=\frac{1}{-4+7i}\times \frac{4+7i}{4+7i}\)

\(=\frac{4+7i}{49i^2-16}\)

\(=\frac{4+7i}{-49-16}\)         \((\because i^2=-1)\)

\(=\frac{-1}{65}(4+7i)\)



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