(1)已知a,b满足a2+b2+4a-8b+20=0,试分解(x2+y2)-(b+axy); (2)计算:(1-1/22)(1-1/32)(1-1/42)…(1-1/20082)(1-1/20092); (3)设a=1999x+1998,b
问题描述:
(1)已知a,b满足a2+b2+4a-8b+20=0,试分解(x2+y2)-(b+axy);
(2)计算:(1-
)(1-1 22
)(1-1 32
)…(1-1 42
)(1-1 20082
);1 20092
(3)设a=1999x+1998,b=1999x+1999,c=1999x+2000,求a2+b2+c2-ab-ac-bc的值.
答
(1)a2+b2+4a-8b+20=0,(a+2)2+(b-4)2=0,所以a=-2,b=4,(x2+y2)-(4-2xy)=x2+y2+2xy-4=(x+y)2-4=(x+y+2)(x+y-2);(2)原式=(1-12)×(1+12)×(1-13)×(1+13)×(1-14)×(1+14)×…×(1-...