How can I prove that is always divisible by 25 when is a whole number greater than zero.
Hello, jeremy5561!
skeeter is right . . . An inductive proof is in order.
Even then, I had difficulty with the inductive step.
Perhaps someone has a better method . . .
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And we must show that is a multiple of 25.
. . That is, that is a multiple of 5.
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But there must be a better way!
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