1.当k取何值时,100x^2-kxy+49y^2是一个完全平方数?

1)K=±2*10*7=±140
2)2^48-1=(2^6)^8-1=64^8-1=(64^4+1)(64^4-1)
=(64^4+1)(64^2+1)(64^2-1)
=(64^4+1)(64^2+1)*65*63
可知能被63整除,也能被65整除
3)x^3+1=(x+1)(x^2-x+1)
4)x^2+1/x^2=(x+1/x)^2-2=2
x^4+1/x^4=(x^2+1/x^2)^2-2=2
5)2006^2-2005*2007=2006^2-(2006^2-1)=1
6)(1-1/2^2)(1-1/3^2)`````(1-1/10^2)
=(1/2*3/2)*(2/3*3/4).(9/10*11/10)
=1/2*11/10=11/20
7) x^2+y^2-4x-2y+5=0,即(x-2)^2+(y-1)^2=0
所以x=2,y=1所以√(x+y)/√(8y-2x)=√3/2
8)a=1,b=-1,另一个因式为x-1

很简单啊，去HAO123就 能查见

1.k取140或-140
化简原式=（10x±7y）方
2. 2^48-1=(2^6)^8-1=64^8-1=(64^4+1)(64^4-1)
=(64^4+1)(64^2+1)(64^2-1)
=(64^4+1)(64^2+1)*65*63
可知能被63整除,也能被65整除
3. 反过来就和以前一样x^3+1=(x+1)(x^2-x+1...