Question

Are the two lines `5x+4y=1` and `4x+5y=7` parallel, perpendicular or neither?

Answer 1

For line `5x+4y=1=>y=-5/4x+1/4` and for line `4x+5y=7=>y=-4/5x+7/5`

because slope for the first is `-5/4` and for the second is
`-4/5` they are neither parallel nor perpendicular.