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If-x-2-9x-2-0-and-x-2-kx-5-0-have-a-common-root-show-that-2k-2-63k-414-0-hence-find-the-value-of-k-such-that-k-gt-9-3-




Question Number 26053 by tawa tawa last updated on 18/Dec/17
If  x^2  + 9x + 2 = 0  and x^2  + kx + 5 = 0  have a common root, show that   2k^2  + 63k − 414 = 0 ,  hence find the value of  k  such that k > 9.3
$$\mathrm{If}\:\:\mathrm{x}^{\mathrm{2}} \:+\:\mathrm{9x}\:+\:\mathrm{2}\:=\:\mathrm{0}\:\:\mathrm{and}\:\mathrm{x}^{\mathrm{2}} \:+\:\mathrm{kx}\:+\:\mathrm{5}\:=\:\mathrm{0}\:\:\mathrm{have}\:\mathrm{a}\:\mathrm{common}\:\mathrm{root},\:\mathrm{show}\:\mathrm{that}\: \\ $$$$\mathrm{2k}^{\mathrm{2}} \:+\:\mathrm{63k}\:−\:\mathrm{414}\:=\:\mathrm{0}\:,\:\:\mathrm{hence}\:\mathrm{find}\:\mathrm{the}\:\mathrm{value}\:\mathrm{of}\:\:\mathrm{k}\:\:\mathrm{such}\:\mathrm{that}\:\mathrm{k}\:>\:\mathrm{9}.\mathrm{3} \\ $$
Answered by kaivan.ahmadi last updated on 18/Dec/17

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