Answer
$-2a-b$
Work Step by Step
To find a product using the distributive property, you take the coefficient and multiply it by each term within the parentheses separately. The negative sign represents a coefficient of $-1$.
The first term within the parentheses is $2a$, so the first term of the product is $-1\times2a$, or $-2a$.
The second term within the parentheses is $b$, so the second term of the product is $-1\times b$, or $-b$.
The terms within the parentheses are connected by a plus sign, so the terms within the product will be too. However, since the term you are adding is negative, and adding a negative is in this case about the same as subtracting a positive, the product can be expressed as a difference (using a minus sign).
The final product, therefore, is $-2a+(-b)$, or $-2a-b$.