作业帮 > 数学 > 作业

设X1,X2是方程2x²-6x+3=0的两个根,利用伟达定理求下列各式的值

来源:学生作业帮 编辑:作业帮 分类:数学作业 时间:2024/11/08 14:01:22
设X1,X2是方程2x²-6x+3=0的两个根,利用伟达定理求下列各式的值
(1)X1²X2+X1X2² (2)(X1-X2)² (3)(X1+1/X2)(X2+1/X1) (4)1/X1²+1/X2²
X1X2=3/2
X1+X2=6/2=3
(1)X1²X2+X1X2²
=X1X2(X1+X2)
=(3/2)*3
=2
(2)(X1-X2)²
=X1^2-2X1X2+X2^2
=X1^2+2X1X2+X2^2-4X1X2
=(X1+X2)^2-4X1X2
=9-6
=3
(3)(X1+1/X2)(X2+1/X1)
=X1X2+1+1+1/X1X2
=3/2+2+2/3
=25/6
(4)1/X1²+1/X2²
=(X1^2+X2^2)/(X1^2X2^2)
=[(X1+X2)^2-2X1X2]/(X1X2)^2
=(9-3)/(9/4)
=8/3