How do you write an equation of a line through (-3,1) and perpendicular to y= -3x+7?
The gradient of
The gradient of a line perpendicular is
To prove this to yourself draw a line with gradient -3 on squared paper and the draw a line at right angles
So the line of the perpendicular will be in the form
But we know it goes through (-3,1)
So substituting those values gives