Answer
$\dfrac{2d - 4}{2d + 1}$
Restriction: $d \ne -\frac{1}{2}$
Work Step by Step
Because both expressions already have a common denominator, we can just simply add the numerators:
$\dfrac{d - 3 + (d - 1)}{2d + 1}$
Use distributive property to get rid of the parentheses. Pay attention to the signs in front of the parentheses:
$\dfrac{d - 3 + d - 1}{2d + 1}$
Combine like terms:
$\dfrac{2d - 4}{2d + 1}$
Now, we need to find the restrictions by seeing what values of the variable will make the denominator equal to zero because if the denominator of any rational expression is zero, the expression is undefined.
To find out the restrictions on the variables, set the denominator equal to zero:
$2d + 1 = 0$
Subtract $1$ from each side:
$2d = -1$
Divide each side by $2$:
$d = -\frac{1}{2}$
Restriction: $d \ne -\frac{1}{2}$