Question

已知A=4x2-4xy+y2,B=x2+xy-5y2, 求(1)A+2B(2)3A-2B

速度点啊

Answer 1

（1）A+2B
＝4x²-4xy+y²+2(x²+xy-5y²)
=4x²-4xy+y²+2x²+2xy-10y²
=6x²-2xy-9y²

(2)3A-2B
=3(4x²-4xy+y²)-2(x²+xy-5y²)
=12x²-12xy+3y²-2x²-2xy+10y²
=10x²-14xy+13y²

Answer 2

解：因为A=4x²-4xy+y²,B=x²+xy-5y²，所以：
（1）A+2B
＝4x²-4xy+y²+2(x²+xy-5y²)
=4x²-4xy+y²+2x²+2xy-10y²
=6x²-2xy-9y²

(2)3A-2B
=3(4x²-4xy+y²)-2(x²+xy-5y²)
=12x²-12xy+3y²-2x²-2xy+10y²
=10x²-14xy+13y²