a: =(căn a-3)^2-b^2
=(căn a-3-b)(căn a-3+b)
b: \(x-9=\left(\sqrt{x}-3\right)\left(\sqrt{x}+3\right)\)
c: \(x-7\sqrt{x}+12=x-3\sqrt{x}-4\sqrt{x}+12=\left(\sqrt{x}-3\right)\left(\sqrt{x}-4\right)\)
d: x*căn x-64
=(căn x)^3-4^3
=(căn x-4)(x+4căn x+16)
\(a-6\sqrt{a}+9-b^2\\ =\left(\sqrt{a}+3\right)^2-b^2\\ =\left(\sqrt{a}+3-b\right)\left(\sqrt{a}+3+b\right)\)
\(x-9=\left(\sqrt{x}-3\right)\left(\sqrt{x}+3\right)\)
\(x-7\sqrt{x}+12\\ =x-4\sqrt{x}-3\sqrt{x}+12\\ =\sqrt{x}\left(\sqrt{x}-4\right)-3\left(\sqrt{x}-4\right)\\ =\left(\sqrt{x}-4\right)\left(\sqrt{x}-3\right)\)
\(x\sqrt{x}+64\\ =\sqrt{x^3}+4^3\\ =\left(\sqrt{x}\right)^3+4^3\\ =\left(\sqrt{x}+4\right)\left(x-4\sqrt{x}+16\right)\)
