x1=[-b+√(b^2-4ac)]/2a
x2=[-b-√(b^2-4ac)]/2a
所以x1+x2=[-b+√(b^2-4ac)-b+√(b^2-4ac)]/2a=-2b/2a=-b/a
x1x2=[-b+√(b^2-4ac)]/2a*[-b-√(b^2-4ac)]/2a
={(-b)^2-[√(b^2-4ac)]^2}/4a^2
=(b^2-b^2+4ac)/4a^2
=c/a
2x^2-6x+3=0
x1+x2=3,x1x2=3/2
x1^2+x2^2=(x1+x2)^2-2x1x2=3^2-2*3/2=6
2010/x1-2010/x2=2010(1/x1-1/x2)
=2010(x2-x1)/x1x2
(x2-x1)^2=(x1+x2)^2-4x1x2=9-6=3
x2-x1=±√3
所以2010/x1-2010/x2=2010*(±√3)/(3/2)
=±1340√3
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