Question

If z= 5i(-3/5i) then z is equal to 3 + bi. The value of b’ is:
a) 1
b)2
c)0
d)3​

Answer 1

Answer:

z = 5i × -3/5 i

⇒ z = -3 i²

⇒ z = +3

Comparing with 3+ bi we get b=0

Ans : C

Answer 2

Given :-

If z = 5i × -⅗i, then z = 3 + bi

To Find :-

Value of b

Solution :-

$\sf z = 5i \times - \dfrac{3}{5}i$

$\sf z = 3 + bi$

$: \implies \sf 5i \times - \dfrac{3}{5} i = 3 + bi$

$: \implies \sf - 5 \times \dfrac{3}{5} \times {i}^{2} = 3 + bi$

$: \implies \sf - 3 \times - 1 = 3 + bi$

$: \implies \sf 3 = 3+ bi$

➪ b = 0

Answer : Option C