Question

Tìm x biết { x +1 } + { x +3 } + { x + 5 } + .... + { x + 9 } = 750

Answer 1

x + 1 + x + 3 +x + 5 + x + 7 + x + 9 = 750

  ( x + x + x + x + x ) + ( 1 + 3 + 5 + + 7 + 9 ) = 750

     x x 5 + 25 = 750

     x x 5 = 750 - 25

     x x  5 = 725

           x = 725 :5

           x = 145

Answer 2

x=750:(1+3+5+7+9)

x=750:25

x=30

Answer 3

x+1+x+3+x+5+...+x+9 

= ( x+x+x+x)+ (1+3+5+9)

=x*5+25=750

  x*5=750-25

  x*5=725

     x= 725:5

     x=145