Answer:
8.8n² + 2n + 0.1
Explanation:
For this expression, all you have to do is combine like terms, which means to combine terms with n² with each other, terms with n with each other, and so on.
7.8n² + 0.5 + 9n - 0.4 - 7n + n²
Now, put the n² terms, n terms, and constants (no n) with each other.
7.8n² + n² + 9n - 7n + 0.5 - 0.4
Now you can add and subtract to combine like terms.
7.8n² + n² + 9n - 7n + 0.5 - 0.4
8.8n² + 2n + 0.1
And that's your answer.