Question:
Express the given complex number in the form $a+i b: 3(7+i 7)+i(7+i 7)$
Solution:
$3(7+i 7)+i(7+i 7)=21+21 i+7 i+7 i^{2}$
$=21+28 i+7 \times(-1)$ $\left[\because i^{2}=-1\right]$
$=14+28 i$
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