Question

化简：（X2+XY+Y2）2 — 4XY（X2+Y2）

Answer 1

原式=[(x²+y²)+xy]²-4xy(x²+y²)

=(x²+y²)²+2xy(x²+y²)+x²y²-4xy(x²+y²)

=(x²+y²)²-2xy(x²+y²)+x²y²

=[(x²+y²)-xy]²

=(x²-xy+y²)²