Question

The equation of the line goes through point (7,8) and is perpendicular to line 4x+5y=4 written in form y=mx+b.... What is m and what is b?

Answer 1

Perpendicular lines have slopes that are negative reciprocals.

You have to find the slope of the given line by putting the equation in y = mx + b form

4x + 5y = 4

5y = -4x + 4
y = (-4/5)x + 4/5

m = -4/5 so the slope of the line perpendicular to this line is 5/4

(Note the two slopes multiply to = -1)

We have the slope m = 5/4
and the point (7,8)

You can find the line by usingL

y = mx +b
8 = (5/4)(7) + b

solve for b.. to answer you question.