若A=x²-3x-6,B=2x²-4x+6,则A-2B=( ) , 2A+B=( )
人气:240 ℃ 时间:2020-04-19 04:51:31
解答
A-2B
=x²-3x-6-2(2x²-4x+6)
=x²-3x-6-4x²+8x-12
=-3x²+5x-18
2A+B
=2(x²-3x-6)+2x²-4x+6
=2x²-6x-12+2x²-4x+6
=4x²-10x-6
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