表达式7: polygon left parenthesis, "X" , left parenthesis, "X" . "x" plus 1 , "X" . "y" , right parenthesis , "X" plus left parenthesis, 1 , "f" prime left parenthesis, "a" , right parenthesis , right parenthesis , right parenthesispolygonX,X.x+1,X.y,X+1,f′a
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表达式8: left parenthesis, "X" . "x" plus "t" , "X" . "y" , right parenthesisX.x+t,X.y
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表达式9: "x" equals "a"x=a
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表达式10: left parenthesis, "X" . "x" plus 1 , "X" . "y" plus "t" "f" prime left parenthesis, "a" , right parenthesis , right parenthesisX.x+1,X.y+tf′a
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表达式11: left parenthesis, "X" . "x" , "t" "f" prime left parenthesis, "a" , right parenthesis , right parenthesisX.x,tf′a
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表达式12: "a" Subscript, "s" , Baseline equals "f" prime left parenthesis, "a" , right parenthesisas=f′a
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表达式13: left parenthesis, "X" . "x" plus 1 , "X" . "y" plus 1 half "f" prime left parenthesis, "a" , right parenthesis , right parenthesisX.x+1,X.y+12f′a
