(1/3x+?)(?+2y)=4y²-1/9x²

问题描述:

(1/3x+?)(?+2y)=4y²-1/9x²

4y²-1/9x²=(2y+1/3 *x)(2y-1/3 *x) (注因式分解)
则易知:(1/3x+2y)(-1/3*x +2y)=4y²-1/9x²