若4x1-3y1=2,4x2-3y2=2
两式相减 4(x1-x2)-3(y1-y2)=0
则(y1-y2)/(x1-x2)=4/3
所以直线的斜率k=4/3
于是直线方程y=(4/3)(x-x1)+y1
=(4/3)x-4x1/3+y1
=(4/3)x-(4x1-3y1)/3
=(4/3)x-2/3