Answer
$q-5t^{2}$
Work Step by Step
$d=a_{n+1}-a_{n}=\left( -9t^{2}+3q\right) -\left( -4t^{2}+2q\right) =\left( -4t^{2}+2q\right) -\left( t^{2}+q\right) =q-5t^{2}$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.