(2x - y)dx + (2y - x)dy = 0
∂(2x - y)/∂y = - 1 = ∂(2y - x)/∂x,这是全微分方程
∫ (2x - y) dx = x² - xy + h(y)
∂[x² - xy + h(y)]/∂y = - x + h'(y)
- x + h'(y) = 2y - x
=> h'(y) = 2y
=> h(y) = y²
所以通解为x² - xy + y² = C
(2x - y)dx + (2y - x)dy = 0
∂(2x - y)/∂y = - 1 = ∂(2y - x)/∂x,这是全微分方程
∫ (2x - y) dx = x² - xy + h(y)
∂[x² - xy + h(y)]/∂y = - x + h'(y)
- x + h'(y) = 2y - x
=> h'(y) = 2y
=> h(y) = y²
所以通解为x² - xy + y² = C