If the zeroes of the quadratic polynomial ax2 + bx + c, c ≠ 0 are equal, then
Given that, the zeroes of the quadratic polynomial ax2 + bx + c , c ≠ 0 are equal
⇒ Value of discriminant (D) has to be zero
i.e. b2 – 4ac = 0
⇒ b2 = 4ac
Since L.H.S. (b2) can never be negative
⇒ R.H.S. also can never be negative.
∴ a and c must have same sign
[∴ if a and c have opposite sign, then a × c will be negative which is not possible.]