Question

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

Answer 1

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