complex numbers question! (3 Viewers)

[Riviet]

Once you're familiar with the equating real and imaginary parts method, you should be able to go straight to the two equations and solving them.

 

[buchanan]

You can just use the formula and do it in 1 line without mucking about with equations.

 

[felixcthecat]

hehe.. i feel like being surrounded by a group of math teachers ><''

riviet... by equating real and im. u get x⁴ - 16x² - 15 = 0

am i rite..? so then u hav to use the quadratic equation AGAIN.. then u'd get the x² answer, and u hav to root that before u get to the answer..

if i'm rite then i think buchanan's equation is so much faster.. but then i've also been told to remember as little equations as u can ^0^.. cuz by the end of the course i'd be too filled with equations?

edit: buchanan..u've already done ur hsc hav u? cuz i'd be soo freaked out if u havn't... =.=

 

[buchanan]

u get x⁴ - 16x² - 15 = 0

am i rite..?

No. x<SUP>4</SUP>-16x<SUP>2</SUP>-15<SUP>2</SUP>=0.

i think buchanan's equation is so much faster

This part is right!

 

[Rax]

LOL Buchanan, nice quote
Yeah when I guess I should have looked into it a bit more then just asking about derivition. Just explaining some stuff I done lately in Ext 2 has been a bit long in its finding. thanks anyhow

 

[Riviet]

so then u hav to use the quadratic equation AGAIN.. then u'd get the x² answer, and u hav to root that before u get to the answer...

There's no need for the quadratic formula, you can simply make a substition for x² and in most cases you should be able to factorise by inspection unless x and y aren't integers.

 

[pLuvia]

Just stick with the equating Re and Im parts, but if you do decide to use it ask your teacher first, or use it at your own risk

 

[buchanan]

Ask them at your own risk. Most maths teachers don't know much about maths. Ha! Ha!

And I bet most of them would not be capable of proving the formula for the square roots of a complex number.

lol you might be right about that haha

Neverthless, here's the MUCH LONGER SOLUTION:

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But wouldn't you prefer my MUCH SHORTER SOLUTION?:

 

[STx]

hmm, im thinking of using that formula in my half yearly, so it is indirectly in the syllabus?

 

[Riviet]

Use at your own risk, but if you want a definite answer, ask your maths teacher and/or head of maths and see if they would approve the use of the formula.

 

[sikeveo]

You can't use that formula in UNSW maths courses. (well it said that in my class test anyway)

 

[Slidey]

We were told we're allowed use that formula in ANU maths courses, because it saves needlessly deriving it each time for a specific case.

I derive it each time because it's automatic and fairly swift. But there's nothing worng with using the formula. Just make sure you know how to derive it.