Question

What is the slope that is perpendicular to `2x+8y=9`?

Answer 1

First you change the equation into the form y=mx+b

`2x` to the other side: `8y=-2x+9`
divide by 8: y = `-1/4x+9/8`
Now the slope of the perpendicular (we'll call it mp):
Reverse the sign and flip the division:
`mp=+4/1=4`