\(=\left\{542-\left[9.\left(64-8\right):2\right]\right\}\)

\(=\left\{542-\left[9.56:2\right]\right\}\)

\(=542-504:2\)

\(=542-252\)

\(=290\)

\(\text{HT nha bn}\)

146 + 121 + 54 +  379

= ( 146 + 54 ) + ( 121 + 379 )

= 200 + 500

= 700

HT

=700 ^^

\(B=3+3^2+...+3^{108}\)

\(B=\left(3+3^2+3^3\right)+\left(3^4+3^5+3^6\right)+...+\left(3^{106}+3^{107}+3^{108}\right)\)

\(B=3\left(1+3+3^2\right)+3^4\left(1+3+3^2\right)+...+3^{106}\left(1+3+3^2\right)\)

\(B=3.13+3^4.13+...+3^{106}.13\)

\(B=13\left(3+3^4+...+3^{106}\right)\)

Ta có : \(13⋮13\)

\(\Rightarrow B=13\left(3+3^4+...+3^{106}\right)⋮13\)

101 nhaaaaaaaaaaaaaaaaaaaaaaaaaa

101 nha bạn

\(A=3+3^2+3^3+...+3^{21}\)

\(A=\left(3+3^2+3^3\right)+\left(3^4+3^5+3^6\right)+...+\left(3^{19}+3^{20}+3^{21}\right)\)

\(A=3\left(1+3+3^2\right)+3^4\left(1+3+3^2\right)+...+3^{19}\left(1+3+3^2\right)\)

\(A=3.13+3^4.13+...+3^{19}.13\)

\(A=13\left(3+3^4+...+3^{19}\right)\)

Ta cs :\(13⋮13\)

\(\Rightarrow A=13\left(3+3^4+...+3^{19}\right)⋮13\)

có :

A = 3 x 3^2 + 3^3 + ... + 3^21 

A = 3 x 1 + 3 x 3 = 3 x 9 + ... + 3^19 x 1 + 3^19 x 3 + 3^19 x 9

A = 3 x (1 + 9 + 3) + ... + 3^19 x (1 + 3 + 9) 

A = 3 x 13 + ... + 3^19 x 13

A chia hết cho 13

vì ƯCLN là 14 nên ta có : 

a = 14m        b = 14n       => (m ; n) = 1

a x b = 294 x 14 = 4116 = 14m . 14n = 14 . 14 . m . n = 196 . m . n

m . n = 4116 : 196 = 21

21 = 21 . 1 = 3 . 7

vì 1 ko là SNT nên m và n ko thỏa mãn

vì (3 ; 7) = 1 nên m và n thỏa mãn

a = 14 . 3 = 42

b = 14 x 7 = 98