\(x^2-xy-xy+y^2\)
\(=\left(x^2-xy\right)-\left(xy-y^2\right)\)
\(=x\left(x-y\right)-y\left(x-y\right)\)
\(\left(x-y\right)\times\left(x-y\right)\)
ta có:
\(x^2-xy-xy+y^2\)
\(=\left(x^2-xy\right)-\left(xy-y^2\right)\)
\(=\left[x.\left(x-y\right)\right]-\left[y.\left(x-y\right)\right]\)
\(=\left(x-y\right).\left(x-y\right)\)