a即係alpha b即係beta
1.
If a and b are the roots of the equation 10x^2-4x-5=0, find the value of the following.
(a+1/b)(b+1/a)
2.
Let c be a constant. If -2 is a root of the equation 5x^2-4x+c=0, find the other root and the value of c.
3.
If a and b are the roots of the equation x^2+9x+4=0, find the value of the following.
a^3+b^3
F.4數學 please help me........
2009-10-06 3:02 am
回答 (1)
2009-10-06 3:14 am
✔ 最佳答案
1) sum of root= ( - b ) / a = a + b = 2/5 a + b = 2 / 5
product of root = c / a = ab = -1/2
a b = -1/2
then (a+1/b)(b+1/a) = ( ab + a + b + 1 ) / (a b)
= ( -1/2 + 2/5 + 1 ) / (-1/2)
= - 1.8
呢個係第1題ans...應該岩既=]
希望幫到你 第 2 , 3 吾想做~~
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