Question

Tính

346 - [ 124 + 30 : ( 5 ^ 8 : 5^7 ) . 2^2.2018^0]

Bài 2

A = 2+2^2+2^3+2^4+...+2^50

B= 3+3^2+3^3+...+3^50

C= 2^2+2^4+2^6+...+2^50

Answer 1

Bài 2:

a: \(A=2+2^2+2^3+...+2^{50}\)

\(\Leftrightarrow2A=2^2+2^3+2^4+...+2^{51}\)

=>\(A=2^{51}-2\)

b: \(B=3+3^2+3^3+...+3^{50}\)

\(\Leftrightarrow3B=3^2+3^3+...+3^{51}\)

\(\Leftrightarrow2B=3^{51}-3\)

hay \(B=\dfrac{3^{51}-3}{2}\)

c: \(C=2^2+2^4+...+2^{50}\)

\(\Leftrightarrow4C=2^4+2^6+...+2^{52}\)

\(\Leftrightarrow3C=2^{52}-4\)

hay \(C=\dfrac{2^{52}-4}{3}\)