Question

1.如果x²+xy=2,y²=xy=7,那么x²+2xy+y²的值是多少?

Answer 1

1.x²+2xy+y²=x²+xy+(y²+xy)=2+7=9

2.(b+c)-(a-d)=b+c-a+d=b+c-(a-d)=2-(-3)=5