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(2000•朝阳区)用换元法解方程(x2+3x+4)(x2+3x+5)=6时,设...
(2000•朝阳区)用换元法解方程(x2+3x+4)(x2+3x+5)=6时,设x2+3x=y,原方程变形为( )
A.y2-9y+14=0
B.y2+9y-14=0
C.y2+9y+14=0
D.y2+9y+16=0
考点分析:
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