已知x1+x2+x3+x4+x5+x6+x7=2010,且x1+x2=x3,x2+x3=x4,x3+x4=x5,x5+x6=x7,问x1+x2+x3=?

题目

已知x1+x2+x3+x4+x5+x6+x7=2010,且x1+x2=x3,x2+x3=x4,x3+x4=x5,x5+x6=x7,问x1+x2+x3=?

答案

x4=x1+2x2 x5=x1+2x2+x1+x2=2x1+3x2 x6=x4+x5=3x1+5x2 x7=x5+x6=5x1+8x2 x1+x2+x3+x4+x5+x6+x7 =x1+x2+x1+x2+x1+2x2+2x1+3x2+3x1+5x2+5x1+8x2 =13x1+20x2=2010 后面随便取了 得数不一定 x1=10 x2=94 则x1+x2+x3=208 ...