表达式3: "y" minus "y" Subscript, 1 , Baseline equals "S" Subscript, "l" "o" "p" "e" , Baseline left parenthesis, "x" minus "x" Subscript, 1 , Baseline , right parenthesisy−y1=Slopex−x1
3
表达式4: "S" Subscript, "l" "o" "p" "e" , Baseline equals "f" prime left parenthesis, "x" Subscript, 1 , Baseline , right parenthesisSlope=f′x1
