Question

Line f and g are perpendicular. If the slope of line f is 4, what is the slope of line g?

Answer 1

a function whose graph is perpendicular to another, has a NEGATIVE RECIPROCAL slope to that function

let's say the slope of f(x) is a/b then the slope of g(x) will be
`\bf slope=\cfrac{a}{{{ b}}}\qquad negative\implies -\cfrac{a}{{{ b}}}\qquad reciprocal\implies - \cfrac{{{ b}}}{a}`

now, notice yours, f is 4, what does that make g's slope then?

Answer 2

Remembering that the slopes of perpendicular lines are opposite reciprocals, we know that the slope of G would have to be (-1/4).