已知A=3x-1,B=4x-1,求4A+2B-3(A+B)的值,其中x=1999

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已知A=3x-1,B=4x-1,求4A+2B-3(A+B)的值,其中x=1999
已知A=3x-1,B=4x-1,求4A+2B-3(A+B)的值,其中x=1999

已知A=3x-1,B=4x-1,求4A+2B-3(A+B)的值,其中x=1999
A=3x-1,B=4x-1
4A+2B-3(A+B)
=4(3x-1)+2(4x-1)-3(3x-1+4x-1)
=12x-4+8x-2-3(7x-2)
=12x-4+8x-2-21x+6
=-x
当x=1999时
原式=-x=-1999

4A+2B-3(A+B)
=4A+2B-3A-3B
=A-B
=3x-1-4x+1
=-x
=-1999

4A+2B-3(A+B)
=4A+2B-3A-3B
=A-B
=3x-1-(4x-1)
=3x-1-4x+1
=-x
=-1999

4A+2B-3(A+B)
=4A+2B-3A-3B
=A-B
=(3x-1)-(4x-1)
=3x-1-4x+1
=-x
=-1999