(x-2)^2 - 9(x+1)^2 = 0
(x-2)^2 - [3(x+1)]^2 = 0
由平方差公式得：[(x-2) + 3(x+1)][(x-2) - 3(x+1)] = 0
整理得：(4x + 1)(-2x - 5) = 0
4x+1=0,-2x-5=0
所以x1 = -1/4 或x2= -5/2
(x-2)的平方-9(x+1)的平方=0 用公式法怎么解?
(x-2)^2 - 9(x+1)^2 = 0
(x-2)^2 - [3(x+1)]^2 = 0
由平方差公式得：[(x-2) + 3(x+1)][(x-2) - 3(x+1)] = 0
整理得：(4x + 1)(-2x - 5) = 0
4x+1=0,-2x-5=0
所以x1 = -1/4 或x2= -5/2