Simplify each of the following and express it in the form a + ib

Question:

Simplify each of the following and express it in the form a + ib :

$(1-i)^{2}(1+i)-(3-4 i)^{2}$

 

Solution:

Given: $(1-i)^{2}(1+i)-(3-4 i)^{2}$

$=\left(1+i^{2}-2 i\right)(1+i)-\left(9+16 i^{2}-24 i\right)$

$\left[\because(a-b)^{2}=a^{2}+b^{2}-2 a b\right]$

$=(1-1-2 i)(1+i)-(9-16-24 i)\left[\because i^{2}=-1\right]$

$=(-2 i)(1+i)-(-7-24 i)$

Now, we open the brackets

$-2 i \times 1-2 i \times i+7+24 i$

$=-2 i-2 i^{2}+7+24 i$

$=-2(-1)+7+22 i\left[\because, i^{2}=-1\right]$

$=2+7+22 i$

$=9+22 i$

 

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