Answer:
options 2, 3 and 5
Explanation:
first of all, because
n²+3n+2n = 6n simplifies to n²+5n = 6n, which simplifies to
n² = n, which is not true for all n not equal to 0 or 1.
option 6 is not a valid reason, as it made a calculation error.
options 1 and 4 make invalid simplifications.