Descriptions 1, 2, 3, and 5 are accurate, though 5 is ambiguous.
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Description 4 goes with (7x)² = 49x², not 7x².
Description 6 goes with 5·8 + x² + (2x + 8) = x² +2x +48, not 40x² +100x +40.
The description for 5 is accurate, but could also be applied to y² + 3(y - 4), which is why it can be considered to be ambiguous. There are a number of ways to resolve the ambiguity, but they were not used here.