點斜式：y-y0=k(x-x0)

y=k(x-x0)+y0

斜截式：y=kx+b

截距式：x/a+y/b=1(ab不等于0)

兩點式：（y-y1/(y2-y1)=(x-x1)/(x2-x1)

y-y1=[(y2-y1)/(x2-x1)]·(x-x1)