Với $x\ge 0$
a/ $x-2\sqrt x\\=(\sqrt x)^2-2\sqrt x\\=\sqrt x(\sqrt x-2)$
b/ $x+3\sqrt x\\=(\sqrt x)^2+3\sqrt x\\=\sqrt x(\sqrt x+3)$
c/ $x+\sqrt x\\=(\sqrt x)^2+\sqrt x\\=\sqrt x(\sqrt x+1)$
d/ $x-\sqrt x\\=(\sqrt x)^2-\sqrt x\\=\sqrt x(\sqrt x-1)$
e/ $x-3\sqrt x\\=(\sqrt x)^2-3\sqrt x\\=\sqrt x(\sqrt x-3)$