Find the slope of the line which is parallel to x + 2y + 3 = 0.

Given,

⇒ x + 2y + 3 = 0

⇒ 2y = -x - 3

⇒ y = $-\dfrac{1}{2}x - \dfrac{3}{2}$

Comparing above equation with y = mx + c we get,

Slope = $-\dfrac{1}{2}$

Since, slope of parallel lines are equal.

Hence, slope of line parallel to x + 2y + 3 = 0 is $-\dfrac{1}{2}$.