数学题4a²-4a+1-4+12a-9a²其中a=-19a²-12ab+4b²-4a²-12ab-9b²,其中a=1/2,b=-1/2
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![数学题4a²-4a+1-4+12a-9a²其中a=-19a²-12ab+4b²-4a²-12ab-9b²,其中a=1/2,b=-1/2](/uploads/image/z/1835441-17-1.jpg?t=%E6%95%B0%E5%AD%A6%E9%A2%984a%26%23178%3B-4a%2B1-4%2B12a-9a%26%23178%3B%E5%85%B6%E4%B8%ADa%3D-19a%26%23178%3B-12ab%2B4b%26%23178%3B-4a%26%23178%3B-12ab-9b%26%23178%3B%2C%E5%85%B6%E4%B8%ADa%3D1%2F2%2Cb%3D-1%2F2)
数学题4a²-4a+1-4+12a-9a²其中a=-19a²-12ab+4b²-4a²-12ab-9b²,其中a=1/2,b=-1/2
数学题4a²-4a+1-4+12a-9a²其中a=-1
9a²-12ab+4b²-4a²-12ab-9b²,其中a=1/2,b=-1/2
数学题4a²-4a+1-4+12a-9a²其中a=-19a²-12ab+4b²-4a²-12ab-9b²,其中a=1/2,b=-1/2
9a²-12ab+4b²-4a²-12ab-9b²,
=5a²-24ab-5b²
=5×1/4-24×1/2×(-1/2)-5×1/4
=(5+24-5)/4
=6
其中a=1/2,b=-1/2
原式=(9a²-12ab+4b²)-(4a²+12ab+9b²)
=(3a-2b)²-(2a+3b)²
当a=1/2,b=-1/2
(3a-2b)²-(2a+3b)²
=(3×1/2-2×-1/2)²-(2×1/2+3×-1/2)²
=25/4-1/4
=6