\(x\left(x-3\right)\left(x-4\right)\left(x-7\right)\\ =\left(x^2-7x\right)\left(x^2-7x+12\right)\\ =\left(x^2-7x+6-6\right)\left(x^2-7x+6+6\right)\\ =\left(x^2-7x+6\right)^2-36\)
Nhận xét:
\(\left(x^2-7x+6\right)^2\ge0\\ \Rightarrow\left(x^2-7x+6\right)^2-36\ge0\\ \Rightarrow C\)