Find the missing term

The sum of - 3x^2 or 3x^2 and 7x^2 is 10x^2

Step-by-step explanation:

"The sum of - 3x^2 or 3x^2 and 7x^2 is 10x^2" is false as it now stands.

If we combine - 3x^2 and 3x^2, we get 0, so:

"The sum of - 3x^2 or 3x^2 and 7x^2 is 10x^2" is equivalent to

"The sum of (expression) and 7x^2 is 10x^2".

Subtracting 7x^2 from both sides yields (expression) = 3x^2.

So: Although "The sum of - 3x^2 or 3x^2 and 7x^2 is 10x^2" is false,

"The sum of 3x^2 and 7x^2 is 10x^2" is true, and the formerly missing term is 3x^2.