Question

[Puca]

Cho:

\(A=2+2^2+...+2^{60}\)CM: A chia hết cho 3, 7, 15

\(B=3+3^3+3^5+...+3^{1991}\)CM: B: chia hết cho 13 và 41

Answer 1

[zZz Cool Kid_new zZz]

\(A=2+2^2+......+2^{59}+2^{60}\)

\(A=2\left(1+2\right)+....+2^{59}\left(1+2\right)\)

\(A=2\cdot3+...+2^{59}\cdot3⋮3\)

Answer 2

[zZz Cool Kid_new zZz]

\(2+2^2+2^3+....+2^{58}+2^{59}+2^{60}\)

\(=2\left(1+2+4\right)+....+2^{58}\left(1+2+4\right)\)

\(=2\cdot7+.....+2^{58}\cdot7⋮7\)