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Given (A=265)(A = 2^{65}) and (B=264+263+262+...+20)(B = 2^{64} + 2^{63} + 2^{62} + ... + 2^0), which of the following is true?

Solution

Correct Option: 4

Given:

A=265A = 2^{65}

B=264+263+262+...+20B = 2^{64} + 2^{63} + 2^{62} + ... + 2^0

To compare A and B, let's look at the relationship between powers of 2:

B=264+263+262+...+20B = 2^{64} + 2^{63} + 2^{62} + ... + 2^0

BB is sum of powers of 2 from 202^0 to 2642^{64}

For a geometric series with first term aa and ratio rr:

Sum = a(1rn)1r\frac{a(1-r^n)}{1-r} where nn is number of terms

Here:

a=20=1a = 2^0 = 1

r=2r = 2

n=65n = 65 (from 202^0 to 2642^{64} is 65 terms)

B=1(1265)12B = \frac{1(1-2^{65})}{1-2}

B=12651B = \frac{1-2^{65}}{-1}

B=2651B = 2^{65} - 1

Therefore:

A=265A = 2^{65}

B=2651B = 2^{65} - 1

AA is greater than BB by 1.

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