\(\left(x-1\right)\left(x-4\right)\cdot\left(x-2\right)\left(x-3\right)+15\)
\(=\left(x^2-5x+4\right)\left(x^2-5x+6\right)+15\)
Đặt \(x^2-5x+4=a\) ta có
\(a\cdot\left(a+2\right)+15\)
\(=\left(a^2+2a+1\right)+14\)
\(=\left(a+1\right)^2+14\ge14\)
Vậy Min biểu thức bằng 14