2+4+6+..........+100
=(2+100)+(4+98)+.........+(50+52)
=102+102+.......+102(có 25 số 102)
=102 x 25
=2550
2+4+6+.....+100= (100+2)*((100-2)/2+1)/2=2550
mình trước nha
7/10= ; 7/100=; 6 38/100=; 2014/1000=; 3/2=; 2/5=; 5/8=; 1 1/4=; 6 38/100=; 600/38=
2/ 2 * 4 + 2/4 * 6 + 2/ 6 * 8 + ....... + 2/ 98 * 100
1+1+2+2+2+3+3+3+4+4+4+5+5+5+6+6+6+7+7+...+99+99+100
tính 2/2*4 + 2/4* 6 + 2/6*8+.....2/98*100
r)18*123+9*4567*2+5310*6 / (2+4+6+...+20+22)+48
d)71+65*4=y+140/y+260
b11:Hãy chứng tỏ rằng :
100 - {1+1/2+1/3+...+1/100} = 1/2+2/3+3/4+...+99/100
4 x 2 : 2 x 3 : 3 x 4 : 4 x........x 100 : 100 + 6 x 1 : 1 x 2 : 2 x 3 : 3 x 4 : 4 x........x 1000 : 1000 x4
giúp nhanh
2-1+4-3+6-5+.............+1000-999
1/2*4+1/4*6+.............+1/98*1000
5/2*4+5/4*6+...........+5/98*100
Tính nhanh 2/2·4+2/4·6+2/6·8+.........+2/96·98+2/98·100
tính nhanh (2/3+3/4+5/6+...+99/100).(1/2+2/3+3/4+...+98/99)-(1/2+1/3+...+99/100).(2/3+2/4+...+98/99)
(5*6+11-41)*(1+2+3+..+100)
(2+4+6+...+100)*(11*7-78-1)
20152015*2016-20162016*2015
