已知A=x^2-2x+1,B=3x^2-2x+5,求当x的绝对值=2时,3A-[(2A-B)-2(A-B)]

问题描述:

已知A=x^2-2x+1,B=3x^2-2x+5,求当x的绝对值=2时,3A-[(2A-B)-2(A-B)]

3A-[(2A-B)-2(A-B)]
=3A-B
=3X^2-6X+3-3X^2+2X-5
=-4X-2
X=2时,原式=-10
X=-2时,原式=6

3A-[(2A-B)-2(A-B)]
=3A-(2A-B-2A+2B)
=3A-B
=3(X^2-2X+1)-3X^2+2X-5
=-4X-2
当X=2时,3A-[(2A-B)-2(A-B)]=-10
当X=-2时,3A-[(2A-B)-2(A-B)]=6
所以,3A-[(2A-B)-2(A-B)]=-10或6