Consider the following expression and the simplified expression. Expression Simplified Expression 3 x squared plus 5 y squared square plus 3 square plus 4 y squared plus 6 9 x squared minus y squared plus 9 Which terms could be in the boxes to make the expressions equivalent?

Combine like terms. The existing x² term is 3x², so the missing x² term must be 6x² to make 9x². The existing y² terms total 5y² + 4y² = 9y², so adding −10y² leaves −y². The constants 3 and 6 already total 9, so choice C makes the expressions equivalent.

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