Question

Which term of the



a.P.8-6i,7-4i,6-2i,...Is purely imaginary?

Answer 1

The 9th term of the A.P. is purely imaginary.

• The A.P. has a common difference of '2i-1'
• So the A.P. can be expanded as 8-6i, 7-4i, 6-2i, 5, 4+2i, 3+4i, 2+6i, 1+8i, 10i
• So we can see the 9th term(10i) is the purely imaginary term
• Hence we write the answer to be the 9th term which is 10i
• This 9th term 10i does not contain any real part is its purely imaginary and it is the answer

Answer 2

Answer:

Step-by-step explanation:

REAL PART=0

8,7,6...

an=a+(n-1)d

0=8+(n-1)(-1)

8-n+1=0

n=9

9th term will be purely imaginary.

im part=0

6,4,2...

an=6 + (n-1)(-2)

6-2n+2=0

2n=8

n=4

4th term is purely real.