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# Scary fp1 question watch

1. given that z=x+iy find the value of x and the value of y such that z+3iz*=-1+31i

Any help would be much appreciated
2. (Original post by Connor_leigh)
given that z=x+iy find the value of x and the value of y such that z+3iz*=-1+31i

Any help would be much appreciated
Just substitute for z. evaluate, and then equate real parts and equate imaginary parts to get two equations in x and y.

Note: z* is x-iy, the conjugate.
3. Got it, thankyou
4. (Original post by Connor_leigh)
Got it, thankyou
5. There's another part in this question further on. Find the modulus of ZW (Not sure how to get modulus on the keyboard) Z=-24-7i W=2-2root3 (Also not sure how to get root signs).

Could you work this out? I got 48+48root3i+14i+7root3 but it seems way off.
Thanks
6. (Original post by Connor_leigh)
There's another part in this question further on. Find the modulus of ZW (Not sure how to get modulus on the keyboard) Z=-24-7i W=2-2root3 (Also not sure how to get root signs).

Could you work this out? I got 48+48root3i+14i+7root3 but it seems way off.
Thanks
That's a bit of a beast.

First thing to note is |zw| = |z| |w|

So, work out the modulus of z, then the modulus of w, and multiply the two.

Ans in spoiler.

Spoiler:
Show

25 x 4 = 100.

PS:
Best to post in the maths subforum, rather than this umbrella forum - lot more maths people there.
Also, quote me if you need a reply - it shows up immediately on the notifications at the top of the screen. I don't often come to this particular forum.
7. (Original post by ghostwalker)
That's a bit of a beast.

First thing to note is |zw| = |z| |w|

So, work out the modulus of z, then the modulus of w, and multiply the two.

Ans in spoiler.
Spoiler:
Show

25 x 4 = 100.

PS:
Best to post in the maths subforum, rather than this umbrella forum - lot more maths people there.
Also, quote me if you need a reply - it shows up immediately on the notifications at the top of the screen. I don't often come to this particular forum.
Ok thanks, I will do. Realised how i completely flunked that last question. The |Z| Is root 24^2+7+2 and then the |W| is root 2^2+2root3^2

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