\(\left(6x+1\right)^2+\left(6x-1\right)^2-2\left(1+6x\right)\left(6x-1\right)\)
\(=36x^2+12x+1+36x^2-12x+1-2\left(6x+1\right)\left(6x-1\right)\)
\(=72x^2+2-2\left(36x^2-1\right)=72x^2+2-72x^2+2=4\)
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\(\left(6x+1\right)^2+\left(6x-1\right)^2-2\left(1+6x\right)\left(6x-1\right)\)
\(=\left(6x+1\right)^2-2\left(6x+1\right)\left(6x-1\right)+\left(6x-1\right)^2\)
\(=\left[\left(6x+1\right)-\left(6x-1\right)\right]^2\) (Hằng đẳng thức số 2)
\(=2^2=4\)
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