若A+B=1,A^2+B^2=7,求-4A+AB-4A
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若A+B=1,A^2+B^2=7,求-4A+AB-4A
若A+B=1,A^2+B^2=7,求-4A+AB-4A
若A+B=1,A^2+B^2=7,求-4A+AB-4A
(A+B)^2=A^2+B^2+2AB=1
=7-2AB= 1
2AB= -6
AB= -3
(A-B)^2=A^2+B^2-2AB=7+6=13
(A-B)=±[根号13]
2A=(A-B)+(A+B) =±[根号13]+1
A=(±[根号13]+1)/2
8A= 4(±[根号13]+1)
-4A+AB-4A=AB-8A= -7±4[根号13]