2lg(x - 3y) = lgx + lg(4y)lg(x - 3y)² = lg(4xy)(x - 3y)² = 4xyx² - 6xy + 9y² - 4xy = 0x²- 10xy + 9y² = 0(x - y)(x - 9y) = 0x = y 或 x = 9y因为 x - 3y > 0 ,x > 0 ,4y > 0所...