If I add x^5+5x^4 is the answer 6x^9?
no,
you cannot add unlike terms. it would just stay as
x^5+5x^4
Had you multipplied them it would have been 5x^9
Your answer does not come from any operation
you cannot add unlike terms. it would just stay as
x^5+5x^4
Had you multipplied them it would have been 5x^9
Your answer does not come from any operation