Chứng minh rằng: x(xy^2 + y) – y(x^2y + x) = 0.
Chứng minh rằng:
x(xy2 + y) – y(x2y + x) = 0.
Ta có x(xy2 + y) – y(x2y + x) = x . xy2 + x . y – y . x2y – y . x
= x2y2 + xy – x2y2 – xy = (x2y2 – x2y2) + (xy – xy) = 0 + 0 = 0 (đpcm)