Adding polynomials is collecting like terms with more kinds of term to collect. These free printable worksheets ask for the result written out term by term — the x² part, the x part and the number — so nothing can hide inside a half-finished answer.
If they get stuck
The answer key prints on a separate page.
The x² terms combine with each other and the x terms with each other, and never across. It is the same rule as collecting like terms one level up, and a child who is secure there mostly needs practice keeping three columns straight rather than a new idea.
Subtraction is where the marks go. (3x² + 5x − 2) − (x² − 4x + 1) means every term in the second bracket changes sign, including the ones that were already negative, and a child who only negates the first term gets an answer that looks plausible. Rewriting the subtraction as an addition of the opposite is slower and it is worth the time.
One question from a sheet like this one, worked a step at a time — with a sentence saying what just happened and why.
Adding and subtracting polynomials, step by step