What is the perpendicular line for y=.4x+4?

Question

anonymous · Answer

To be fair, there are infinitely many perpendicular lines to that equation.
But anyway, for two lines to be perpendicular, the product of their slopes are -1.

Let's call the slope of the new line a.

this means that a * 4 = -4, meaning a = -1
So the slope of the new line is -1.

The intersection with the Y-axis could be anything, though. They'd still be perpendicular

anonymous · Answer

Okay, pretty much, there was a question that said a line, y=5/2x, and I had to find a perpendicular line that passed through, (10,0). I got y=.4+4, but I didn't know if that was right. I can'texactly remember how to find slope. I'm homeschooled. Haven't studied that in a year and a half, even though it should be easy.. :c

phi · Answer

you're pretty close.  You want the negative reciprocal of 5/2  
that means - 2/5  or -0.4  (not + 0.4)
for the slope
if the line goes through (10,0)
y - 0 =  -2/5(x - 10)
y = -2/5 x + 4

anonymous · Answer

Oh.. Thanks. I think I get it now. c: