The jump from -25 to -15 is +10
The jump from -15 to -5 is also +10
The jump from -5 to 5 is also +10
Unfortunately, this pattern doesn't hold up. The jump from 5 to 10 is +5
Because the gap isn't the same each time, this tells us the sequence is not arithmetic.
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We can show the sequence isn't geometric either. Pick any term to divide it over its previous term
-15/(-25) = 0.6
-5/(-15) = 0.333 approximate
The result isn't the same, so we don't have a common ratio and that's why this sequence isn't geometric.
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It seems like your teacher made a typo. Please double check with them to make sure that they typed the correct sequence. I have a feeling that 10 should be 15, but I'm not entirely sure.