A=2+2^2+...........+2^60

c\m c\h cho 3:2+2^2+....+2^60=2.(1+2)+........+2^59(1+2)

                                             =2.3+.........+2^59.3

                                              =(2+...+2^59).3

                                              =>A chia hết cho 3

cau tiếp tuong tu

3

cô harry porter hery money nói chung nhiều lắm mình ko nhớ

tớ làm nhầm

ban do thieu ma

ta co x+y+3/z=y+z+1/x=x+z+2/y=1/x+y+z, theo tinh chat cua day ti so bang nhau ta co

x+y+3/z=y+z+1/x=x+z+2/y=1/x+y+z=(3+1+2)+2x+2y+2z/z+y+x=6+2(x+y+z)/x+y+z=8

suy ra 1/x+y+z=8 suy ra x+y+z=1/8(1)

ta co x+y+3/z=y+z+1/x=x+z+2/y=8

suy ra x+y+3/z+1=y+z+1/x=x+z+2/y+1

suy ra x+y+z+3/z=y+z+x+1=x+z+y+2/y=9(2)

the (1) vao (2) ta co

1/8+3/z=1/8+1/y=1/8+2/x

suy ra 25/8/z=9/8/y=17/8/x

suy ra z=25/8:8=25/64

y=9/8:8=9/64

x=17/8:8=17/64

nho nhe