Question

Tìm x để 

( x + 2 ) + ( 4 + x ) + ( 6 + x ) + .........+ ( 52 + x ) = 780

 

Answer 1

( x + 2 ) + ( 4 + x ) + ( 6 + x ) + ... + ( 52 + x ) = 780

( x + x + x .... + x ) + ( 2 + 4 + 6 + ... + 52 ) = 780

     26 chữ số x

26 x X + 702 = 780

26 x X = 780 - 702

26 x X = 78

X = 78 : 26

X = 3

Answer 2

Phá ngoặc có:26x+702=780

\(\Rightarrow\)x-3