化简求值 2m-(-3n+(4n-2(3m-n)+5n))其中m=-(1/2) n=-1
2个回答
展开全部
2m-(-3n+(4n-2(3m-n)+5n))
= 2m-(-3n+(4n-6m-2n+5n))
=2m-(-3n+4n-6m-2n+5n)
=2m+3n-4n+6m+2n-5n
=(2+6)m+(3-4+2-5)n
=8m-4n
=8x(-1/2)-4x(-1)
=-4+4
=0
= 2m-(-3n+(4n-6m-2n+5n))
=2m-(-3n+4n-6m-2n+5n)
=2m+3n-4n+6m+2n-5n
=(2+6)m+(3-4+2-5)n
=8m-4n
=8x(-1/2)-4x(-1)
=-4+4
=0
追问
已知A=3a^2-2a+1,B=5a^2-3a+2，求3A-2B
追答
3A-2B
=3(3a²-2a+1)-2(5a²-3a+2)
=(9a²-6a+3)-(10a²-6a+4)
=9a²-6a+3-10a²+6a-4
=-a²-1
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