수식 8: "m" equals StartFraction, left parenthesis, "f" left parenthesis, "a" plus "h" , right parenthesis minus "f" left parenthesis, "a" , right parenthesis , right parenthesis Over "h" , EndFractionm=fa+h−fah
8
수식 9: "y" equals "m" left parenthesis, "x" minus "a" , right parenthesis plus "f" left parenthesis, "a" , right parenthesisy=mx−a+fa