1.若x=156,y=144,½x²;+xy+½y²等于?2.25(a+b)²-16(a-b)²等于?

问题描述:

1.若x=156,y=144,½x²;+xy+½y²等于?2.25(a+b)²-16(a-b)²等于?

,½x²;+xy+½y²=½(x²+2xy+y²)=½(x+y)²=½×300²=45000原式=[1.5(a+b)]²-[4(a-b)]²=(1.5a+1.5b)²-(4a-4b)²=[(1.5a+1.5b)+(4a-4b...