Question

The equation of a line is given below.
y=-4x-9
What is the equation of a line perpendicular to the given line?

Answer 1

The slope of the perpendicular line will be the negative reciprocal of the slope of the above line. So first find the slope 'm' of the above line. The perpendicular line will have the slope -1/m.

Answer 2

if your looking for the reciprocal of a number, you must know that it means 1 must be over the given number. Example: reciprocal of x is 1/x

Answer 3

Finding the slope of a line perpendicular to the given line (y=-4x-9) is straightforward, as ranga and Zale have explained. It's 1/4.
Now any line perpendicular to this line y=-4x-9 will have the slope 1/4. Without knowing a specific point through which the new (perpendicular) line is to pass, we can only write a generic equation for the new (perp.) line: y = (1/4)x + b, where be can be any constant (including zero).