a²+a-2=6,求2a²-a+1的值
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a²+a-2=6,求2a²-a+1的值
a²+a-2=6,求2a²-a+1的值
a²+a-2=6,求2a²-a+1的值
解a²+a-2=6
即a²+a=8
2a²-a+1
=2(a²+a)-3a+1
=2*8-3a+1
=17-3a
由a²+a-8=0
即a=(-1+√33)/2或a=(-1-√33)/2
即
2a²-a+1
=17-3a
=17-3*(-1+√33)/2
=17+3/2-3√33/2
=37/2-3√33/2
或
2a²-a+1
=17-3a
=17-3*(-1-√33)/2
=17+3/2+3√33/2
=37/2+3√33/2
35/2+3/2*(根号33)或者35/2-3/2*(根号33)