\(A=4+4^2+4^3+...+4^{100}\)
\(4A=4^2+4^3+...+4^{1001}\)
\(4A-A=\left(4^2+4^4+...+4^{1001}\right)-\left(4+4^2+...+4^{1000}\right)\)
\(3A=4^{1001}-4\)
\(A=\dfrac{4^{1001}-4}{3}\)
C = 1 - 5 + 52 - 53 + ... + 5200
5C = 5 - 52 + 53 + ... + 5201
C + 5C= (1 - 5 + 52 - 53 + ... + 5200 ) + ( 5 - 52 + 53 + ... + 5201)
6C = 1 + 5201
C = \(\dfrac{1+5^{201}}{6}\)
B = \(1-2\) + \(2^2+2^3+...+2^{1000}\)
\(2B=2-2^2+2^3-...+2^{1001}\)
\(B+2B=\)(\(1-2\) \(+\)\(2^2+2^3+...+2^{1000}\)) +( \(2-2^2+2^3-...+2^{1001}\))
\(3B=1+2^{1001}\)
\(B=\dfrac{1+2^{1001}}{3}\)
a, \(A=4+4^2+4^3+...+4^{1000}\)
\(4A=4^2+4^3+4^4+...+4^{1001}\)
\(4A-A=\left(4^2+4^3+4^4+...+4^{1001}\right)-\left(4+4^2+4^3+...+4^{1000}\right)\)
\(3A=4^{1001}-\text{4}\Rightarrow A=\dfrac{4^{1001}-4}{3}\)
c, \(C=1-5+5^2-5^3+...+5^{200}\)
\(5C=5-5^2+5^3+...+5^{201}\)
\(6C=1+5^{201}\)
\(C=\dfrac{1+5^{201}}{6}\)