Saturday, December 18, 2010

Given that 1/x1+1/x2=2, what is t such as x^2-(t-2)x+t+1=0?

It is given that 1/x1 + 1/x2 =
2.


t has to be determined such that x^2 - (t-2)x + t +1 =
0


1/x1 + 1/x2 = 2


=>
(x1 + x2)/x1*x2 = 2


For a quadratic equation ax^2 + bx + c
= 0 with roots x1 and x2,


c/a = x1*x2 and -b/a = x1 +
x2


Here the equation is x^2 - (t-2)x + t +1 =
0


=> (t - 2)/(t + 1) =
2


=> t - 2 = 2t +
2


=> t =
-4


The required value of t =
-4

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