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Mathematics 7 Online
OpenStudy (itiaax):

HELP WITH COMPLEX NUMBERS. *question attached below* Will give medal and fan :)

OpenStudy (itiaax):

Can I have some help on this problem, please?

OpenStudy (mathmath333):

any idea u have?

OpenStudy (itiaax):

None :(

OpenStudy (mathmath333):

first put the values z=x+iy in the fraction (z+i)/(z+2)

OpenStudy (mathmath333):

then arrange the numerator and denomintor in (a+bi) form

OpenStudy (mathmath333):

for example the denominator comes a+(c+d)i then rationalize the denominator using a-(c+d)i

OpenStudy (mathmath333):

then rearrange the result in a+bi form

OpenStudy (mathmath333):

as it is given im(z+i)/(z+2)=0, therefore bi will be zero

OpenStudy (mathmath333):

that is the imaginary part will be zero

OpenStudy (itiaax):

For the first part, I ended up with ](x+i(y+1)/(x+2)+iy] =0

OpenStudy (mathmath333):

so multiply the numerator and denominator with [(x+2)-iy] to rationalize the denominator

OpenStudy (itiaax):

Give me a sec to work it out :)

OpenStudy (itiaax):

I ended up with: x^2+2x+2iy+y^2+ix+2i+y

OpenStudy (mathmath333):

where is the denominator?

OpenStudy (itiaax):

Oh let me do that one now :$ sorry

OpenStudy (itiaax):

The denominator is x^2+y^2+4x+4

OpenStudy (mathmath333):

ok now arrange numerator in (a+bi) form

OpenStudy (itiaax):

[(x^2 + y^2 +2x +y) + ((2iy+ix+2i)] ?

OpenStudy (mathmath333):

no , u have to take out 'i' common like a+(c+d)i and it also seems wrong in calculation

OpenStudy (itiaax):

Wouldn't a be the real part/the real values?

OpenStudy (mathmath333):

yes it would be

OpenStudy (itiaax):

[(x^2 + y^2 +2x +y) + (i(2y+x+2)]

OpenStudy (mathmath333):

well i came up with x^2+y^2+2x+y+i(x+2y-xy+2)

OpenStudy (mathmath333):

check if u hve done it wrong

OpenStudy (itiaax):

This is what Wolfram Alpha gave me: x^2+i (x+2 y+2)+2 x+y^2+y

OpenStudy (mathmath333):

ok sry so now write it with denominator in the form a+bi

OpenStudy (mathmath333):

as real part dosn't matter here so write only imaginary part=0

OpenStudy (mathmath333):

and note real part too ,it will helpful for 2nd question

OpenStudy (itiaax):

I'm a bit confused :S

OpenStudy (mathmath333):

why

OpenStudy (itiaax):

I don't understand why the imaginary part =0

OpenStudy (mathmath333):

lol , it is given 0 cuz u will get equation of straight line from that

OpenStudy (itiaax):

Okay. So, we're writing the denominator in the form a+ib now?

OpenStudy (mathmath333):

no denominator doesnt have i ,u have to numerator /denominator and then arrange in (a+bi) form

OpenStudy (itiaax):

So then, we have (x^2+i (x+2 y+2)+2 x+y^2+y)/(x^2+y^2+4x+4)

OpenStudy (mathmath333):

yes seperate it like( a/b )+(c/d)i

OpenStudy (itiaax):

:S

OpenStudy (itiaax):

How can I do that?

OpenStudy (mathmath333):

lol (x^2+2 x+y^2+y)/(x^2+y^2+4x+4)+i (x+2 y+2)/(x^2+y^2+4x+4)

OpenStudy (mathmath333):

oops sry it will not equal to 1,lol

OpenStudy (mathmath333):

just put i (x+2 y+2)/(x^2+y^2+4x+4)=0 and calculate

OpenStudy (mathmath333):

as imagnery part is zero for que 1

OpenStudy (itiaax):

When I paste this into the solver it is giving me an error

OpenStudy (mathmath333):

put in wolfram

OpenStudy (itiaax):

Wolfram gave me the same equation I put in :O

OpenStudy (mathmath333):

u will get (x+2 y+2=0)

OpenStudy (mathmath333):

see in the solution part

OpenStudy (mathmath333):

thus its a straight line proved.

OpenStudy (mathmath333):

for question 2, (x^2+2 x+y^2+y)/(x^2+y^2+4x+4)=0

OpenStudy (mathmath333):

that is (x^2+2 x+y^2+y)=0

OpenStudy (mathmath333):

its the standard equation of circle

OpenStudy (mathmath333):

check its centre and radius

OpenStudy (mathmath333):

it will match with that given in the question

OpenStudy (itiaax):

Yup :)

OpenStudy (mathmath333):

yo so how u feel now was that easy

OpenStudy (itiaax):

Yup, very :D

OpenStudy (itiaax):

One question, though..did we ignore the Im and the Re?

OpenStudy (mathmath333):

i cant get?

OpenStudy (mathmath333):

what u trying to say

OpenStudy (itiaax):

Like in the question where it said Im(z+i/Z+2) and Re(z+i/z+2)

OpenStudy (mathmath333):

yes we only work on the data given

OpenStudy (mathmath333):

dont care about anything else

OpenStudy (itiaax):

Alrighty. Thank you sooooo much for your time, help and patience :)

OpenStudy (mathmath333):

\(\Huge\tt \color{black}{\ddot\smile}\)

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