AC方程y=1/3(x-1)+1=1/3x+2/3
点B到AC距离d=|m-3根号m+2|/根号10
|AC|=根号[(1-4)^2+(1-2)^2]=根号10
ABC面积S=1/2*d*|AC|=1/2|m-3根号m+2|=1/2|(根号m-1)(根号m-2)|=1/2[-(根号m-3/2)^2+1/4]
AC方程y=1/3(x-1)+1=1/3x+2/3
点B到AC距离d=|m-3根号m+2|/根号10
|AC|=根号[(1-4)^2+(1-2)^2]=根号10
ABC面积S=1/2*d*|AC|=1/2|m-3根号m+2|=1/2|(根号m-1)(根号m-2)|=1/2[-(根号m-3/2)^2+1/4]