Final answer:
To simplify the given expression, first combine like terms and reorder the terms. Then, group the terms with the same variable and factor out the common factors. The final simplified expression is p(p+3q)-q(6p-9).
Step-by-step explanation:
To simplify the expression p²+9q²-6pq-9q+3pp²+9q²-6pq-9q+3p, we first combine like terms.
We have p²+3p+9q²-6pq-9q. We can further simplify this by reordering the terms: p²+3p-6pq+9q²-9q.
Now, we group the terms with the same variable: (p²+3p-6pq)+(9q²-9q).
Finally, we can factor out the common factors in each group: p(p+3q-6q)+(9q-9).
The simplified expression is therefore p(p+3q)-q(6p-9).