tmua.me Extreme Set A Paper 2 · Question 18

For real numbers $x$ and $y$ , define

s_n=x^n+y^n

for each positive integer $n$ .

Consider the condition that $s_1$ , $s_2$ and $s_4$ are integers, and the statement that $s_n$ is an integer for every positive integer $n$ .

Which of the following correctly describes the condition in relation to the statement?

AThe condition is necessary but not sufficient.

BThe condition is sufficient but not necessary.

CThe condition is both necessary and sufficient.

DThe condition is neither necessary nor sufficient.

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