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Mathematics 21 Online
OpenStudy (anonymous):

Please help! :)

OpenStudy (anonymous):

kay

OpenStudy (luigi0210):

\(i^2=-1\)

OpenStudy (anonymous):

-6-17i

OpenStudy (anonymous):

i think

OpenStudy (whpalmer4):

@bbcream14 not correct

OpenStudy (anonymous):

okay then give me a sec

OpenStudy (anonymous):

So.. i^10 = -1 ?

OpenStudy (whpalmer4):

yes. \[i^{10} = i^2*i^2*i^2*i^2*i^2 = (-1)(-1)(-1)(-1)(-1) = -1\]

OpenStudy (anonymous):

Okay now what?

OpenStudy (anonymous):

hint: compute [(1 - i)^2 ]^5

OpenStudy (anonymous):

Yeah but these are the answers.. -32i -32 + 32i 32 32 -32i

OpenStudy (anonymous):

-.- those are the answers AFTER you do some simplification

OpenStudy (anonymous):

i'll give you the next hint: (1-i)^2 = 1 - 2i + i^2, and i^2 = -1

OpenStudy (anonymous):

Oh okay.

OpenStudy (anonymous):

i dont get where you got the 1 - 2i + 1^2 ...

OpenStudy (anonymous):

because you foil (1-i)^2 you'll get 1 - 2i + i^2 since i^2 = -1, you have 1 - 2i - 1 = -2i and so (-2i)^5 = (-2)^5 * i^5 = -32i

OpenStudy (anonymous):

Oh duh

OpenStudy (whpalmer4):

Or you could expand \[(1-i)^{10} = i^{10}-10 i^9+45 i^8-120 i^7+210 i^6-252 i^5+210 i^4-120 i^3\]\[\qquad+45 i^2-10 i+1\] and simplify :-)

OpenStudy (anonymous):

Still trying to understand the rest haha

OpenStudy (whpalmer4):

This is definitely a problem where thinking a bit first will save you a lot of effort!

OpenStudy (anonymous):

Yes! haha can you help me with another one? i still dont understand it fully

OpenStudy (anonymous):

(-√3 + i)^6

OpenStudy (anonymous):

Im still trying to understand this though.. (1−i)10=i10−10i9+45i8−120i7+210i6−252i5+210i4−120i3 +45i2−10i+1

OpenStudy (anonymous):

Can you help me with this one? (-√3 + i)^6 ]

OpenStudy (whpalmer4):

If you multiply out \[(1-i)^{10}=(1-i)(1-i)(1-i)(1-i)(1-i)(1-i)(1-i)(1-i)(1-i)(1-i)\]that's what you'll get....but then those various powers of \(i\) simplify to \[-1-(-10i)+45 +120i \text{ etc.}\]

OpenStudy (anonymous):

Ohhh okay i get it :)

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