Evaluate:
`int_(-1)^(4)3dx`

Explanation

To evaluate the integral \( \int_{-1}^{4} 3 \, dx \), we can follow these steps:

### Step 1: Set up the integral
We start with the integral:
\[ I = \int_{-1}^{4} 3 \, dx \]

### Step 2: Factor out the constant
Since 3 is a constant, we can factor it out of the integral:
\[ I = 3 \int_{-1}^{4} dx \]

### Step 3: Evaluate the integral of \( dx \)
The integral of \( dx \) is simply \( x \). Therefore, we have:
\[ I = 3 [x]_{-1}^{4} \]

### Step 4: Apply the limits of integration
Now we need to evaluate \( x \) at the upper limit (4) and the lower limit (-1):
\[ I = 3 [4 - (-1)] \]

### Step 5: Simplify the expression
This simplifies to:
\[ I = 3 [4 + 1] = 3 \times 5 \]

### Step 6: Calculate the final result
Finally, we calculate:
\[ I = 15 \]

Thus, the value of the integral \( \int_{-1}^{4} 3 \, dx \) is \( 15 \).

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