(−x 2 −4x−3)+(x 2 +5x+7)

The given expression is:

(−x^2 −4x−3)+(x^2 +5x+7)

To simplify this, we combine like terms.

The x^2 terms are -x^2 and x^2. When you add these together, they cancel each other out because -x^2 + x^2 equals 0.

The x terms are -4x and 5x. When you add these together, you get 1x.

The constant terms are -3 and 7. When you add these together, you get 4.

So, the simplified expression is:

1x + 4