Question

bài 3:

A=4+2²+2³+....+2³⁰

Answer 1

\(A=4+2^2+2^3+2^4+.......+2^{30}\)

\(A=2+2+2^2+2^3+........+2^{30}\)

\(A=2.\left(1+2^2+2^3+2^4+......+2^{29}\right)\)

Answer 2

\(A=2+2^2+2^3+2^4+....+2^{30}\)

\(A=2\left(1+2+2^2+2^3+......+2^{29}\right)\)

\(2A=2+2^2+2^3+2^4+......+2^{61}\)

Answer 3

\(A=2+2+2^2+2^3+....+2^{30}\)

\(A=2\left(2+2^2+2^3+......+2^{29}\right)\)

\(2A=2+2^2+2^3+2^4+......+2^{31}\)

\(A=2A-A=\left(2+2^2+2^3+....+2^{31}\right)-\left(2+2^2+2^3+.........+2^{30}\right)\)

\(A=\frac{2^{31}-1}{2-1}\)