Question

If a, b, c are non-zero real numbers and az² + bz + c + i = 0 has purely imaginary roots, then a equals –

• A. bc²
• B. b²c
• C. –b²c
• D. –bc²

Answer 1

Answer: (B)

b²c

Answer 2

Sol. Let ia is root where a Ī R

–aa² + ba + c + i = 0

Ž c = aa², 1 + ba = 0

Ž a² = c/a , a =$\frac{- 1}{b}$

Ž $\frac{1}{b^{2}}$= $\frac{c}{a}$Ž a = b²c