解方程x²+4xy-4y²=0
问题描述：
解方程x²+4xy-4y²=0
答
x²+4xy-4y²=0
x² + 4xy + 4y² - 8y² = 0
(x + 2y)² - 8y² = 0
(x + 2y + 2√2y)(x + 2y - 2√2y) = 0
x + 2y + 2√2y = 0
x = -2(1+√2)y
x + 2y - 2√2y = 0
x = 2(√2-1)y