Joseph L.

asked • 01/08/20

Write the expression as a complex number in standard form

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Barry M. answered • 01/08/20

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Looks like 2 different answers. So I'll take a shot at it.


Referring to Julian's answer, the 2nd expression should be 16 + 1 in the denominator, not 4 + 1.

That gives (25 + 19i)/17 = 25/17 + (19/17)i


So now there are 3 answers!!!

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Barry M.

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I have to retract this answer, since 7 + 3i and 4-i were not in ( ). You first divide 3i/4, then add and subtract the other terms.
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01/08/20

Julian O.

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I made my correction. I agree with your answer, Barry.
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02/13/20

Barry M.

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In retrospect, it's not really clear if the student posted the problem correctly. It could very well be that the problem had 7 and 3i in a numerator, as in my fist solution and Julian's revised solution, but we really don't know. It could have been as posted, in which case my retraction and John's answer would still hold.
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02/13/20

John M. answered • 01/08/20

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7+3i/4-i = (28 - 3i -4i)/4 = (28 - i)/4 = 7 - .25i

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Julian O.

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Don't you rationalize the denominator?
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01/08/20

Julian O.

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I believe the denominator is 4 - i.
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01/08/20

Barry M.

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That's a good question. I don't see how the steps were obtained. And even if the expression to the right of the first equals sign had been correct, -3i and -4i would combine to make -7i, and the answer would then be 7 - (7/4)i. But cross multiplying would prove it's not right.
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01/08/20

Barry M.

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However, looking at it again, the way the problem is written, there's no () around the 7 + 3i and 4 - i (maybe they intended it). So following PEMDAS, John is right!! 7 + 0.75i - i = 7 - .25i
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01/08/20

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