complex numbers help!!?

Question

the complex number a+bi is a pure imaginary number when:
1) a=0 and b=0
2) a=0 and b does not =0
3) a does not = 0 and b does not = 0
4) a does not = 0 and b = 0

wat is the answer and why....please explain i dont understand the question....thanx for any help in advance

Answer 1

(2) -- you have 0+bi = bi, a pure imaginary number.

For (1), you have 0+0i = 0.
For (3), you have a+bi which is not a pure imaginary number.
For (4), you have a+0i = a which is a real number.

Answer 2

2

Answer 3

A complex number (a + bi) have a real part (a) and an imaginary part (bi), where i = sqrt (-1)

A pure imaginary occurs when a = 0 of course, then,

2) Is the good one

Answer 4

a +bi is a pure imaginary number if and only if a =0 and b not equal to zero

ib = pure imaginary number ( b different from 0) for all other values of b

Answer 5

2) a=0 and b does not =0
Reason: 0+bi = bi, a pure imaginary number.

Answer 6

answer is 2)
when a is 0 you have just bi which is pure imaginary because there is no real component.

Answer 7

A complex number a+ bi is pure imaginary
when it is of the form bi. That means a = 0
and b .ne. 0, choice 2).

Answer 8

2)

Because is a is the real component so to have pure imaginary you can't have any real.