Advanced Math practice question

Answer: -16

The squares share 16x² + 1; only the cross terms differ: −8x − (+8x) = −16x, so k = −16.

Common wrong answers

If you answered 0

The x² and constant terms cancel, but the cross terms add to −16x.

If you answered 16

The first square has the smaller cross term: −8x − 8x = −16x, negative.

If you answered -8

Each square contributes a cross term of size 8x; the difference doubles it.

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