Perform indicated operation (simplify as a+bi)

**Hapa** · April 12th 2009, 04:07 PM

1 + 4i / 1 - i

Thanks in advance!

**mr fantastic** · April 12th 2009, 04:23 PM

Originally Posted by Hapa

1 + 4i / 1 - i

Thanks in advance!

Is it (1 + 4i)/(1 - i), that is, $\frac{1 + 4i}{1 - i} ?$ Please be less ambiguous when you post.

**Hapa** · April 12th 2009, 04:26 PM

My apologies. Yes, it is as you listed

(1 + 4i) / (1 - i)

**e^(i*pi)** · April 12th 2009, 04:28 PM

Originally Posted by Hapa

My apologies. Yes, it is as you listed

(1 + 4i) / (1 - i)

Use the difference of two squares $a^2-b^2 = (a-b)(a+b)$
and $i^2 = -1$ to rationalise the denominator

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Thread: Perform indicated operation (simplify as a+bi)