Let line L_1 be the graph of 5x + 8y = -9. Line L_2 is perpendicular to line L_1 and passes through the point (10,-10). If line L_2 is the graph of the equation y=mx +b, then find m+b.
Rearranging line L_1 into intercept form, y = -5/8x - 9/8 If line L_2 is perpendicular, it would have slope 8/5, y = 8/5x + b
Plugging in (10, -10),
-10 = 16 + b
b = -26
Therefore m+b is 8/5 + (-26) = -24.4 or -24 2/5