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1.已知:x+1/x=6,那么x²+1/x²=2.已知:A=2x²-x+1,A-2B=x-1,求B+A要过程.
题目详情
1.已知:x+1/x=6,那么x²+1/x²= 2.已知:A=2x²-x+1,A-2B=x-1,求B+A
要过程.
要过程.
▼优质解答
答案和解析
(1)
x²+1/x²
=(x+1/x)²-2
=6²-2
=34
(2)
A=2x²-x+1
A-2B=x-1
2x²-x+1-2B=x-1
2x²-x+1-x+1=2B
2B=2x²-2x+2
B=x²-x+1
于是
B+A=x²-x+1+2x²-x+1=3x²-2x+2
=
x²+1/x²
=(x+1/x)²-2
=6²-2
=34
(2)
A=2x²-x+1
A-2B=x-1
2x²-x+1-2B=x-1
2x²-x+1-x+1=2B
2B=2x²-2x+2
B=x²-x+1
于是
B+A=x²-x+1+2x²-x+1=3x²-2x+2
=
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