Answer
No.
Work Step by Step
$21(2-5x)+37(3x)-6(7+x)=0$, thus they are not linearly independent, thus they cannot be a basis.
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.