Hey there! :)
(x³ - 2x² + 4) + (2x³ + x² - 2)
To simplify this, let's first get rid of all the parenthesis.
Please remember that : a positive times a negative is a negative, and a negative times a negative is a positive! :)
So, using the above knowledge, let's get to simplifying!
x³ - 2x² + 4 + 2x³ + x² - 2
Now, let's look at our variables/numbers. Note that we have some like terms in here. So, let's add like terms!
(x³ + 2x³) + (-2x² + x²) + (4 - 2)
Simplify.
3x³ + (-x²) + (2)
Now, get rid of our parenthesis [read above about multiplying positives/negatives if you are confused about what is about to happen].
3x³ - x² + 2
~Hope I helped!~