Q6 of 30 Page 36

If one zero of the polynomial 4x2 – 8kx – 9 is the negative of the other. Find the value of k?

The polynomial 4x2 – 8kx – 9 is quadratic hence it will have two zeroes


Let one zero of polynomial be α


As the other one is negative hence it would be –α


Thus, α and –α are roots of 4x2 – 8kx – 9


Compare 4x2 – 8kx – 9 with ax2 + bx + c = 0


a = 4, b = –8k and c = –9


Sum of roots of quadratic =



Substituting the value of b and a



⇒ 8k = 0


⇒ k = 0


Hence k = 0


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