tim x,y thuoc N* biet 1+x+x^2+x^3=2^y
tim x, y thuoc N biet:
1! + 2! +3! +....+ x! = y2
a,tim x biet |x-2|+|3-2x|=2x+1
b,tim x,y thuoc Z biet xy+2x-y=5
c, tinh A=(1-1/15)(1-1/21)(1-1/28).....(1-1/210)
tim x;y thuoc z biet:
1/x + 1/y = 1/5
tim cac so x,y,z thuoc Q biet rang (x+y):(5-z):(y+z):(y+9)=3:1:2:5
tim x;y thuoc Z biet (2*x+5*y+1)*(2|x|+y+x2+x)=105
a, Tim x biet:/x-2/+/3-2x/=2x+1
b, Tim x,y thuoc Z biet:xy+2x-y=5
c, tim x,y,z, biet :2x=3y;4y=5zva 4x-3y+5z=7
a)Tim x, y thuoc Q biet:
(x-1)^2+(y+1)^2=0
b)Tim x, y biet:
2^x+1 × 3^y = 12^x
tim x, y thuoc N de 1! + 2! + ... + x! = y!