Question

Tìm X:

(X+1)+(X+5)+(X+9)+...+(X+29)=960

Answer 1

\(\left(x+x+..+x\right)+\left(1+5+9+...+29\right)=960\)

\(15\times x+225=960\)

\(15\times x=735\)

\(x=49\)

Answer 2

\(\left(x+x+..+x\right)+\left(1+5+9+...+29\right)=960\)

\(15\times x+225=960\)

                                                                                      

\(15\times x=735\)

\(x=49\)

Answer 3

{ x + 1 } + { x + 5 } + { x + 9 } + ........+ { x + 29 } = 960

= { x + x + x } + { 1 + 5 + 29 } = 960

=> 960 = 15 X x + 225 = 960

=> 15 X x = 735

=> x = 735 : 15 = 49

=> Vậy nên x = 49