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已知ax^2+bx+1=0，解1.x1^3+x2^3 2.x1/x2+x2/x1 3.x1^2/x2^2+x2^2/x1^2

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3 | 2011-10-4 13:28:57 | 显示全部楼层 |阅读模式

x1+ x2 = -b/ax1x2 = c/a1.x1^3+x2^3= (x1+ x2)[(x1+x2)2 -3xy]= -b/a（b2/a2 -3c/a）2.x1/x2+x2/x1 =[(x1+x2)2-2x1x2]/x1x2= (b2/a2 -2c/a)/(c/a)= b2/ac - 23.x1^2/x2^2+x2^2/x1^2= (x1^4 + x2^4)/(x1x2)^2=[ (x1^2 + x2^2)^2 - 2(x1x2)^2]/(x1x2)^2={[ (x1 + x2)^2 - 2x1x2] - 2(x...

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