表达式6: "a" equals left bracket, 1 , ... , "n" , right bracketa=1,...,n
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表达式7: "n" equals 12n=12
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表达式8: left parenthesis, "x" minus StartFraction, "a" Over "n" , EndFraction , right parenthesis squared plus "y" squared equals left parenthesis, StartFraction, "a" Over "v" Subscript, "m" "a" "c" "h" , Baseline "n" , EndFraction , right parenthesis squaredx−an2+y2=avmachn2
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表达式9: left parenthesis, "x" minus "k" , right parenthesis squared plus "y" squared equals left parenthesis, StartFraction, "k" Over "v" Subscript, "m" "a" "c" "h" , Baseline , EndFraction , right parenthesis squaredx−k2+y2=kvmach2
