If you would like to solve (5 * x^3 + 3 * x^2 - 5 * x + 4) + (8 * x^3 - 5 * x^2 + 8 * x + 9), you can calculate this using the following steps:
(5 * x^3 + 3 * x^2 - 5 * x + 4) + (8 * x^3 - 5 * x^2 + 8 * x + 9) = 5 * x^3 + 8 * x^3 + 3 * x^2 - 5 * x^2 - 5 * x + 8 * x + 4 + 9 = 13 * x^3 - 2 * x^2 + 3 * x + 13
The correct result would be 13 * x^3 - 2 * x^2 + 3 * x + 13.
Shoutout to @neuron
Your answer is: 13x^3 - 2x^2 + 3x + 13
Have an amazing day and stay hopeful!