If the zeroes of the quadratic polynomial ax2 + bx + c, where c≠0, are equal, then

the zeroes of a quadratic polynomial are equal when discriminate is equal to 0

i.e. D = 0


b2 - 4ac = 0


4ac = b2


ac = b2/4 > 0 (square of any positive or negative number is positive )


ac > 0


For ac > 0, a and c must have the same sign


i.e., either a > 0 and c > 0 or a < 0 and c < 0

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