-6\(\sqrt{ }\)2

x.x.....x+(2+4+....+200)=302.x

100.x+(200+2).[(200-2):2+1]:2=302.x

100.x+202.100:2=302.x

202.50=302.x-100.x

202.50=(302-100).x

202.50=202.x

x=50

=>x=50

30

=>x thuộc ƯCLN(48,60)

             48=2⁴.3

             60=2².3.5

=>ƯCLN(48,60)=2².3=12

=>x=12

3.(x-1)=2-(-25)

3.(x-1)=27

x-1=27:3

x-1=9

x=9+1

x=10

=>x=10

M=(5+5²)+(5³+5⁴)+....+(5⁷⁹+5⁸⁰)

M=5.(1+5)+5³.(1+5)+.....+5⁷⁹.(1+5)

M=5.6+5³.6+.......+5⁷⁹.6

M=6.(5+5³+5⁵+.....+5⁷⁹)        (vì 6 chia hết cho 6)

=>M chia hết cho 6

=> x thuộc ƯCLN(16,28)

      16=2⁴

      28=2².7

=>ƯCLN(16,28)=2²=4

vậy x=4

=14

 = 29.(9+13-29)

= 29.(-7)

= -203

= 3