Advanced Math practice question

Answer: 6

(3x)² = 9x², and 9x² − 3x² = 6x². So k = 6.

Common wrong answers

If you answered 0

0 treats (3x)² as 3x².

If you answered 3

3 comes from (3x)² = 6x², doubling instead of squaring the 3.

If you answered 9

9 forgets to subtract the 3x².

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