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WebGraphing.com Forum » List all forums » Forum: Precalculus and Trigonometry Homework Help » Thread: Irrational Numbers Question |
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Total posts in this thread: 2 |
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EternalSummer247
USA Joined: Jul 6, 2007 Posts: 36 Status: Offline |
Ok, so I bought this cool book on Pre-Calculus and am just now getting started. Chapter One is a refresher course and here is the only problem I'm having so far... If a= 3+2i and b= 1+4i and i= sqrt(-1) then ab= ? Ok so I set this up as 3+2[sqrt(-1)][1+4[sqrt(-1)] I can't remember how to deal with the square root of a negative number, can't remember if I need to foil this thing or what! Please help! Thanks, Jason |
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pskinner
Joined: Apr 2, 2005 Posts: 694 Status: Offline |
You want to foil it. I just write i and use the fact that i^2=-1: (3+2i)(1+4i)=3*1+3*4i+2i*1+2i*4i=3+12i+2i+8i^2=3+14i+8(-1)=-5+14i. ---------------------------------------- Principal Skinner |
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Irrational Numbers Question
Re: Irrational Numbers Question