Complex Numbers Help

snoreborewhore

I'm not the best at maths, hence why I'm doing Ordinary Level, and right now I'm revising complex numbers - one of my weakest areas. I'm currently doing Question 4 from the 1998 paper 1 as revision and I can't seem to get my head around a part of it. The marking scheme/solutions for that year aren't available online so I'm desperate. Can anyone help?

Q. Verify that 4-3i is a root of z^2 - 8z +25 = 0

Thanks!

lostatsea

Solution shown here: http://www.studentxpress.ie/ordpapers/ordcompsoln1998.pdf

snoreborewhore

lostatsea wrote: »

Solution shown here: http://www.studentxpress.ie/ordpapers/ordcompsoln1998.pdf

Thank you so much!

Raeone

You sub 4-3i instead of z, and then just keep working it out.
If you end up with 0=0 then it means that 4-3i is a root of it.
If you end up with another number = 0 then, it is not.

snoreborewhore

Raeone wrote: »

You sub 4-3i instead of z, and then just keep working it out.
If you end up with 0=0 then it means that 4-3i is a root of it.
If you end up with another number = 0 then, it is not.

Got it, it worked out!

Bears and Vodka

Also, since it says verify if you get something other than 0=0 it means you went wrong somewhere! Most likely the -9i^2 bits. People forget to change the sign sometimes.

snoreborewhore

Thanks for all the help!