a)theo mik là sai đầu bài
b)2+4+6+8+...+2x=210
2.(1+2+3+...+x)=210
(1+2+3+...+x)=210:2=105
=>x.(x+1):2=105
=>x=14
Vậy x=14
a) x+(x+1)+(x+2)+(x+3)+.....+(x+2010)=20229099
=>x+x+1+x+2+x+3+.....+x+2010=20229099
=>(x+x+...+x) (có 2011 c/s x) +(1+2+3+....+2010)=20229099
=>2011.x+(2010-1):1+1=20229099
=>2011x+(2011+1).2009:2=20229099
=>2011x+2021054=20229099
=>2011x =20229099-202154
=>2011x =18280045
=>x =18280045:2011
=> x =9
vậy,x=9
a) (x + x + x + ... + x) + (1 + 2 + 3 + ... + 2010) = 20229099
2011x + (1 + 2010) + (2 + 2009) + ... + (1005 + 1006) = 20229099
2011x + 2011 + 2011 + ... + 2011 = 20229099
2011x + 2011.1005 = 20229099
2011x + 2021055 = 20229099
2011x = 20229099 - 2021055
2011x = 18208044
x = 9054,223
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