Let P 1, P2 is two points on the straight line L, and P is different from P 1 on L. If any point of P2 is P 1(x 1, y 1), P2(x2, y2), λ is a real number, and λ = vector. Through the coordinate operation of vectors, p 1 = (x-x 1, y-y 1) and p2 = (x2-x, y2-y) ∴ (x-x65438+. λ=(x-x 1)/(x2-x)λ=(y-y 1)/(y2-y)∴λ=(x-x 1)/(x2-x)∴λx2-λx