write down the equation of a line perpendicular to y=5x+3?

I put y=-5x+3 but the teacher said its wrong
Thanks

Question

write down the equation of a line perpendicular to y=5x+3?


I put y=-5x+3 but the teacher said its wrong
Thanks

.sam. · Answer

Of course its wrong, :)
the gradient is 5,so to find the perpendicular line use the formula $$m_{1}+m_{2}=-1$$
5m=-1
m=-1/5

.sam. · Answer

the equation should be $$m_{1}m_{2}=−1$$ not $$m_{1}+m_{2}=−1$$

.sam. · Answer

once you have ,m=-1/5, apply to any coordinate (since you didnt specify any coordinate)
At   (8,0)

$$y-y_{1}=m(x-x_{1})$$
y=-1/5 x + 1/5 +8
y=-1/5 x +41/5

callisto · Answer

At   (8,0)
$$y-y_{1}=m(x-x_{1})$$
y-0 = -1/5 (x-8)
y = -1/5x + 8/5

.sam. · Answer

whoops made a mistake there
y−y1=m(x−x1)
y=-1/5 x + 8/5

katielong · Answer

no, we haven't done anything like that before... i dont think that would be it

anonymous · Answer

The teacher is right. Your doing negative reciprocal with perpendicular problems.
(For example, the negative reciprocal of 4 is -1/4)
You the negative reciprocal for slope only.