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It is given that $${\text{(}}{{\text{2}}^{32}} + 1)$$ is exactly divisible by a certain number, which one of the following is also definitely divisible by the same number ?
Answer & Solution
Correct Answer:
Option
A
$$\eqalign{
& {{\text{a}}^3} + {b^3} = (a + b)({{\text{a}}^2} + {b^2} - ab) \cr
& {\text{Take option (A)}} \cr
& {\text{ = }}{{\text{2}}^{96}} + 1{\text{ }} \cr
& = {({2^{32}})^3} + {(1)^3} \cr
& = ({{\text{2}}^{32}} + 1)[{({2^{32}})^2}{\text{ + }}{{\text{1}}^2}{\text{ - }}{{\text{2}}^{32}}] \cr
& = ({{\text{2}}^{32}} + 1)[{2^{64}} + 1 - {2^{32}}] \cr
& {\text{Clearly, }} \cr
& {{\text{2}}^{32}} + 1{\text{ is a factor of }}{{\text{2}}^{96}} + 1 \cr} $$
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