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Help with FP1 chapter 1, Mixed exercise 1L, Queston 9b (LAST QUESTION OF CHAPTER 1)

Heyy just need some help with the explanation of the answer in solving Question 9b , 9a is straight forward, I have the FP1 CD and i dont get how they derived the answer. Maybe someone can enlighten me

FP1, Mixed Exercise 1I, Question 9)

z= a+3i/2+ai aER

a) Given that a=4, find |z|.

b) Show that there is only one value of 'a' for which arg z= π/4 , and find this value.

P.S pretty ergent wanna finally finish this chapter off! xD

(edited 9 years ago)

Reply 1

BabyMaths

Original post by cyrusdagreat

You can multiply the numerator (and denominator) by the conjugate of the denominator. The resulting denominator itself won't matter as it will be real.

You need to find the value of a for which the real part of (a+3i)(2-ai) is equal to the imaginary part..they also need to be positive.