Given that α is a common root of the equations x^2 + kx - 3 = 0 and 2x^2 + kx - 12 = 0
(a) Show that α = -6/k
(b) Find k
一條F.4 Quadratic equation 急急急急
2011-09-23 5:09 am
回答 (1)
2011-09-23 5:18 am
✔ 最佳答案
a)α² + kα - 3 = 0 .....(1)2α² + kα - 12 = 0 .....(2)(1)*2 - (2) :kα - 6 + 12 = 0α = - 6 / kb)Putting α = - 6 / k to (1) :(- 6 / k)² + k(- 6 / k) - 3 = 036 / k² - 9 = 0k² = 4 k = 2 or - 2
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