2 + 4 + ..... + 2x = 110
2x = 110 - ( 2 + 4 + .... + 18)
2x = 110 - 90
2x = 20
=> x = 0
2 + 4 + 2x = 110
2x = 110 - ( 2 + 4 + ... + 18 )
2x = 110 - 90
2x = 20
x = 20 : 2
x = 10
2 + 4 + 6 + ...... + 2x = 110
2.( 1 + 2 + 3 + ..... + x ) = 110
1 + 2 + 3 +....... + x = 110 : 2
1 + 2 + 3 + ........ + x = 55
=> ( x + 1 ) . x : 2 = 55
=> ( x + 1 ) . x = 55 . 2
=> ( x + 1 ) . x = 110
=> ( x + 1 ) . x = 11 . 10
=> x = 10
đừng kb vs nó, nó là thằng lừa dối tình bạn
