Maths

x^3-9x+10=0
( x - 2 ) ( x^2 + 2x – 5 ) = 0
x = 2 or x = { -2 ± [ 2^2 – 4 X 1 X (-5) ]^(1/2) } / 2
x = 2 or x = -1 ± 6^(1/2)

2009-06-09 16:17:25 補充：
x = 2 or x = 1.4495 or -3.4495

2009-06-09 16:19:12 補充：
Let f(x) = x^3-9x+10
then f(2) = 0
therefore x - 2 is a factor of x^3-9x+10
i.e x^3-9x+10 = ( x - 2 ) ( x^2 + 2x – 5 )

2009-06-09 16:21:52 補充：
When you factorize x^3-9x+10

The possible values for testing are : ±1, ±2, ±5, ±10


f(1) and f(-1) are not zero, but f(2) = 0 !

x3-9x+10=0
(x-2)(x2+2x-5)=0
x-2=0 or x2+2x-5=0
x=2 or x2+2x+1=6
x=2 or(x+1)2=6
x=2 or x+1=√6)or x+1/2=-√6)
x=2 or x=-1+√6 or x=-1-√6)

2009-06-09 16:18:19 補充：
x=2 or x+1=√6or x+1/2=-√6

x=2 or x=-1+√6 or x=-1-√6

The answer :X=2/1.449