原式=4(x-1)²+4(x+1)(x-1)+(x+1)²=[2(x-1)+(x+1)]²=(3x-1)²
4(x-1)²-4(1-x²)+(1+x)²=4(x-1)²-4(1-x)(1+x)+(1+x)²=4(x-1)²+4(x-1)(1+x)+(1+x)²=[2(x-1)+(1+x)]²=(2x-2+1+x)²=(3x-1)²
=4x²-8x+4-4+4x²+1+2x+x²=9x²-6x+1=(3x-1)²
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