急~~解一題不等式.....

2007-07-02 9:10 pm
-2X^2-6X+9>0

請寫下詳細過程....TX

X^2+4X+1>0

回答 (1)

2007-07-02 9:52 pm
✔ 最佳答案
1. -2X^2-6X+9>0
-(-2X^2-6X+9)>0x-1
2X^2+6X-9>0
use the quadratic formular 1or2
[quadratic formular 1: -b +/- (square root b^2-4ac)/2a (When ax^2+bx+c)]
[quadratic formular 2: -b' +/- (square root b'^2-ac)/a (When ax^2+2b'x+c)]
a=-2 ,b=6 ,c=9
quadratic formular 1: 6 +/- (square root 36+72)/-4
X=6+/-square root 108/-4
=3+/-square root 27/-2

therefore ,-2X^2-6X+9>0

X^2+4X+1>0
use the quadratic formular 1or2
a=1 ,b=4 ,c=1
quadratic formular 2: -2+/-(square root 4-1)/1
X=-2+/-square root 3

therefore ,X^2+4X+1>0


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