Advanced Math practice question

Answer: 4

Using a² − b² = (a − b)(a + b) with a = 1 + √2 and b = 1 − √2: (2√2)(2) = 4√2. So k = 4.

Common wrong answers

If you answered 0

0 assumes the two squares are equal; they differ in the cross term.

If you answered 2

2 halves the result, forgetting one factor of 2.

If you answered 8

8 doubles the result.

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