Question

用直接开平方法解 9(y-1)²=4（3y-1）²

carrot55
3（y-1)=±2(3y-1)
为什么2前面要写± 3前面不用写±呀

Answer 1

9(y-1)²=4（3y-1）²
3（y-1)=±2(3y-1)
3y-3=6y-2或3y-3=-6y+2
y=-1/3或y=5/9

Answer 2

9(y-1)²=4（3y-1）²
3²(y-1)²=2²（3y-1）²
[3(y-1)]²=[2(3y-1)]²
3(y-1)=±2(3y-1)]