Answer
The solution is $\Big(-\infty,-\dfrac{1}{2}\Big)$
Work Step by Step
$2x+1\lt0$
Take the $1$ to the right side of the inequality:
$2x\lt-1$
Take the $2$ to divide the right side:
$x\lt-\dfrac{1}{2}$
Express using interval notation:
The solution is $\Big(-\infty,-\dfrac{1}{2}\Big)$
