(y+3)(1-3y)=5+y²-3y^2-8y+3=5+y^24y^2+8y+2=0y^2+2y+1/2=0(y+1)^2=1/2y+1=±√2/2y=-1±√2/2 你这题,用因式分解法啰嗦(y+3)(1-3y)=5+y²-3y^2-8y+3=5+y^24y^2+8y+2=0y^2+2y+1/2=0(y+1)^2-(√2/2)^2=0(y+1-√2/2)(y+1+√2/2)=0y=√2/2-1或y=-√2/2-1这个算是因式分解法了吧?