Chapter 2 - Section 2.3 - Writing Equations of Lines - 2.3 Exercises - Page 172: 19

$y=x-1$

A $y-$intecept of $( 0,-1 )$ implies that $b= -1 .$ Using $y=mx+b$ or the slope-intercept form of linear equations where $b$ is the $y-$intercept and $m$ is the slope, the equation of the line with $m= 1 ,$ and $b= -1 $ is \begin{array}{l}\require{cancel} y=x-1 .\end{array}