\(A=\left(x-1\right)\left(x-3\right)\left(x-4\right)\left(x-6\right)+10\)
\(A=\left(x-1\right)\left(x-6\right)\left(x-3\right)\left(x-4\right)+10\)
\(A=\left(x^2-7x+6\right)\left(x^2-7x+12\right)+10\)
\(A=\left(x^2-7x\right)^2+18\left(x^2-7x\right)+72+10\)
\(A=\left(x^2-7x\right)^2+18\left(x^2-7x\right)+82\)
\(A=\left(x^2-7x\right)^2+2\left(x^2-7x\right).9+9^2+1\)
\(A=\left(x^2-7x+9\right)^2+1\)
Vì \(\left(x^2-7x+9\right)^2\ge0\)
\(\Leftrightarrow\left(x^2-7x+9\right)^2+1\ge1\)
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