原式=4(x+1)²-7(x-1)(x+1)+3(1-x)²
=4(x+1)²-7(x+1)(x-1)+3(x-1)² 把(x+1)和(x-1)看成整体,用十字相乘法分解
=[2(x+1)-(x-1)] [2(x+1)-3(x-1)]
=(2x+2-x+1)(2x+2-3x+3)
=(x+3)(5-x)
当x=1/2时：
原式=(1/2+3)(5-1/2)
=7/2×9/2
=63/4