(Y1-Y)/(Y2-Y1)=(X1-X)/(X2-X1)
y=kx+m, y1=kx1+m y2=kx2+m, k=(y2-y1)/(x2-x1) m=y1-(y2-y1)*x1/(x2-x1) y=(y2-y1)/(x2-x1)x+(y1*(x2-x1)-x1(y2-y1))/(x2-x1) (y1-y2)x+(x2-x1)y+(x1y2-x2y1)=0, a=y1-y2, b=x2-x1, c=x1y2-x2y1,
A、描绘图象时取坐标单位的时候不能随意,要使得大部分点落在整个坐标区域中.故AD错误; B、描完点后,先大致的判断这些点是不是在一直线,然后画一直线,让这些点均匀的散落这条直线的两侧.故B错误,C正确; 故选:C.