Line $l_1$ represents the graph of $3x + 4y = -14$. Line $l_2$ passes through the point $(-5,7)$, and is perpendicular to line $l_1$. If line $l_2$ represents the graph of $y=mx +b$, then find $m+b$.
Rewrite l_1 in the form y = -(3/4)x - 14/4 Its slope is -3/4, which means the slope of a line perpendicular to it has slope m = +4/3.
Thus, line L_2 can be written as y = 4x/3 + b
If it goes through point (-5, 7) then we must have 7 = 4*(-5)/3 + b.
Can you take it from here?