Question

If a + 2b > 5c and quadratic equation ax² + 2bx – 5c = 0 has imaginary roots then –

• A. a > 0, c > 0
• B. a > 0, c < 0
• C. a < 0, c > 0
• D. a < 0, c < 0

Answer 1

Answer: (B)

a > 0, c < 0

Answer 2

Let f(x) = ax² + 2bx – 5c

given f(1) > 0 so graph must be as shown in figure

so f(x) > 0 " x Ī R

\ f(0) > 0 Ž – 5c > 0

Ž c < 0 & a > 0