2【a-1】²-12【a-1】+18 【x²-2xy+y²】+【-2x+2y】+1

来源：学生作业帮编辑：搜搜考试网作业帮分类：数学作业时间：2024/06/24 00:29:55

2【a-1】²-12【a-1】+18 【x²-2xy+y²】+【-2x+2y】+1
a²-8ab+16b²
x+y=0.2,x+3y=1 求3x²+12xy+12y²的值
1.2【a-1】²-12【a-1】+18
2.【x²-2xy+y²】+【-2x+2y】+1
3.a²-8ab+16b²
4.x+y=0.x+3y=1 求3x²+12xy+12y²的值

2【a-1】²-12【a-1】+18
=2【（a-1）²-6（a-1）＋9】
=2（a-1-3）²
=2（a-4）²
【x²-2xy+y²】+【-2x+2y】+1
=（x-y）²-2（x-y）＋1
=（x-y-1）²
a²-8ab+16b²
=(a-4b)²
x+y=0.2,x+3y=1
相加,得
2x＋4y=1.2
x＋2y=0.6
所以
3x²+12xy+12y²
=3(x²＋4xy＋4y²)
=3(x+2y)²
=3×0.6²
=1.08

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