3a*3a+3a^2+3a^2-(4a)^2

If you want to simplify, you get \(-a^2\)

Can you show how you calculated that? Thank you so much for a quick answer.

(3a * 3a) + (3a² + 3a²) - (4a)²

That is the same thing as:

(3a * 3a) + (3a² + 3a²) - (4a*4a)

Multiply 3a times 3a and 4a times 4a:

(9a²) + (3a² + 3a²) - (16a²)

The parenthesees are not necessary.

9a² + 3a² + 3a² - 16a²

These terms are all alike. They can be combined.

9 apples + 3 apples + 3 apples - 16 apples = -1 apples

9a² + 3a² + 3a² - 16a² = -1a² = -a²

Simplify the following:
3×3 a a + 3 a^2 + 3 a^2 - (4 a)^2

Multiply each exponent in 4 a by 2:
3×3 a a + 3 a^2 + 3 a^2 - 4^2 a^2

4^2 = 16:
3×3 a a + 3 a^2 + 3 a^2 - 16 a^2

3 a×3 a = 3×3 a^2:
3×3 a^2 + 3 a^2 + 3 a^2 - 16 a^2

3×3 = 9:
9 a^2 + 3 a^2 + 3 a^2 - 16 a^2

9 a^2 + 3 a^2 + 3 a^2 - 16 a^2 = -a^2:
Answer: |-a^2