Q7 of 30 Page 36

If one zero of the polynomial ax2 + bx + c is double the other then show that 2b2 = 9ac?

Let one zero of polynomial ax2 + bx + c be α


The other zero is double hence 2α


Sum of roots of quadratic





Product of roots of quadratic




Substituting value of α from (i)





⇒ 2b2 = 9ac


Hence proved


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