Let A and B be constants such that the graphs of the lines x + 5y = 7 and 15x + Ay = B are perpendicular and intersect at (-8,3). Enter the ordered pair (A,B).
+128408 x + 5y =7
15x + Ay = B
The slope of the first line = -(1/5)
So..since the lines are perpendicular ..the slope of the second line must be = 5
This implies that -15/A = 5 ⇒ A = -3
If the lines intersect at (-8, 3)......the for the second line,
15(-8) + -3(3) = B
-120 - 9 = B
B = -129
So the equation of the second line must be
15x - 3y = -129
So (A, B) = (-3 -129)
Here's a graph : https://www.desmos.com/calculator/zyizjg9kkt
