不解方程组{2m+n=6.m-3n=1},求7n(m-3n)^2-2(3n-m)^3的值

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不解方程组{2m+n=6.m-3n=1},求7n(m-3n)^2-2(3n-m)^3的值

7n(m-3n)^2-2(3n-m)^3
=7n(m-3n)^2+2(m-3n)^3
=(7n+2m-6n)(m-3n)
=(2m+n)(m-3n)
=6*1
=6