To simplify the expression 2(a^2 + ab) - 3ab, let's first substitute the given values: a = 2 and b = -1.

1. Substituting the values:

We have 2(2^2 + 2(-1)) - 3(-1).
Simplifying further, we get 2(4 - 2) + 3.
This becomes 2(2) + 3.

2. Simplifying the expression:

Now we can simplify the expression by performing the multiplication and addition operations.

2(2) + 3 = 4 + 3 = 7.

So, the simplified expression is equal to 7.

3. Explanation:

The given expression is 2(a^2 + ab) - 3ab.
We substitute the values a = 2 and b = -1 to simplify the expression.
After substituting the values, we simplify the expression by performing the necessary calculations.
In this case, we first calculate the values inside the parentheses, a^2 + ab, which gives us 4 + (-2) = 2.
Then we multiply this result by 2, which gives us 2(2) = 4.
Next, we calculate -3ab, which becomes -3(-1) = 3.
Finally, we add the results of the two calculations, 4 + 3 = 7.
Therefore, the simplified expression is equal to 7.

In summary, when a = 2 and b = -1, the expression 2(a^2 + ab) - 3ab simplifies to 7.