Question 958660
For the first two, what is the question?
Please repost with additional information.
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The third one looks like a series starting at -9 and increase by 2.
{{{a[n]=-9+2(n-1)=-9+2n-2=-11+2n}}}
So when {{{n=18}}},
{{{a[18]=-11+2(18)}}}
{{{a[18]=-11+36}}}
{{{a[18]=25}}}