(с-3)(с+4)-с²

To simplify the expression \((c-3)(c+4) - c^2\), follow these steps:

1. First, expand the expression \((c-3)(c+4)\):

   \[ (c-3)(c+4) = c \cdot c + 4c - 3c - 12 = c^2 + c - 12 \]

2. Now, substitute this back into the original expression:

   \[ (c^2 + c - 12) - c^2 \]

3. Now, simplify the expression by subtracting \(c^2\):

   \[ c^2 + c - 12 - c^2 = c - 12 \]

So, the simplified expression is:

\[ c - 12 \]