Question 111

A number $$1 + 7^{47}$$ is divisible by $$x$$ . Which of the following is also divisible by $$x$$?

Solution

Check with each of the options,

$$7^{141} + 1$$ can be written as $$\left(7^{47}\right)^3+1^3$$

$$a^3+b^3=\left(a+b\right)\left(a^2+b^2-ab\right)$$

So, $$7^{141} + 1$$ is $$\left(7^{47}+1\right)\left(7^{94}+1-7^{47}\right)$$

Hence, option B is the correct answer.

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