Explanation:
The first term has its exponents add to 1+2 = 3
The second term has its exponents add to 1+1 = 2
The third term can be written as -2x^0y^0, and those exponents add to 0
The sums count down: 3, 2, 0
So standard form means we write the terms with the largest degree sums first, then second largest and so on.
