在实数范围内因式分解

题目

在实数范围内因式分解
x2+3x-7
x2+3y2
x2+2xy-5y2
x2+3xy-7y2
2分之一-2xy+y2

答案

x^2+3x-7=(x+3/2)^2-37/4=(x+3/2+genhao37/2)(x+3/2-genhao37/2)
x^2+2xy-5y^2=(x+y)^2-6y^2=(x+y+genhao6 y)(x+y-genhao6 y)
x^2+3xy-7y^2=(x+3/2 y)^2-37/4 y^2=(x+3/2y+genhao37 y/2)(x+3/2y-genhao37 y/2)