có x+(x+1)+(x+2)+....+(x+30) = 1240
x+x+1+x+2+......+x+30 = 1240
(x+x+x+...+x) + ( 1+ 2+....+30) = 1240
31 số x
31.x + ( 30 +1) . 30 : 2 = 1240
31.x + 465 = 1240
31.x = 1240 - 465
31.x = 775
x = 775 :31
x= 25
Vậy x=25
tim x thuoc N biet
x+(x+1)+(x+2)+(x+3)+.......+(x+30)=1240
1+2+3+.....+x=210
Tim x thuoc stn
a, x + ( x +1) + ( x + 2 )+........+ (x +30)+1240
b,1+2+3 + ........ + x+210
Tim so nguyen x biet
x + (x + 1) + (x + 2) + ... + (x + 30) = 1240
tim X thuon N ,biet :
a,x+(x+1)+(x+2)+........+(x+30)=1240
b, 1+2+3+4+........+ x =210
TIM x THUOC Z , BIET :
a) / 2x + 1 / = 7
b) 3/x + 1 / + 1 = 27
c) 20 = 20 + 19 + 18 + 17 + ..... + x
d) x + ( x+ 1 ) + ( x + 2 + ...... + 29 + 30 = 30
tim x thuoc Z biet:
a, -x + 28 = 34
b, -57 - (11 - x) = 8
c, 30 - |-x - 30| = 0
Tim x, y thuoc Z biet : | x-2| + (x-y+1)^2 =0
tim x thuoc Z biet :
(x-1)^2 =(x-3)^4
HELP ME:0!!
tim x thuoc z biet x+5:x-2
