<PRE><B>Question 269921</B>
Find the equation of line through 18,15 parallel to -8x+5y=3 and perpindicular. 
I get the slope is 8/5 parallel and -5/8 perp, please help with the rest of the formula.There answer is (-5/8)x+(105/4) and -(-8/5)x+(-69/5). How are they getting the two answers?

You have the two slopes right :)

The slope-intercept frm of the paralle line is:

y = (8/5)*x + b

Since the line passes through (18,15) we know when x = 18, y = 15 so:

15 = (8/5)*18 + b
b = 144/5 - 15
b = 144/5 - 75/18
b = 69/5 

So the parallel line is: y =(8/5)*x + 69/5

The perpendicular line is:

y = (-5/8)*x + b
15 = (-5/8)*18 + b
b = -90/8 - 15
b = -90/8 - 120/8
b = -210/8
b = -105/4

So the perpendicular line is: y = (-5/8)*x - 105/4</PRE>