Question

Write an equation of a line that is (a) parallel to the given line and (b) perpendicular to the given line. Where the given line is x= -4 ;

I got An equation of a line parallel to the x axis is y=-4x+3, and An equation of a line perpendicular to the x axis is x=4 is this right? If not what would be a better answer?

Answer 1

(a) x = 10

(b) y = 4

Explanation:

For a line of the form y = mx + b, the slope is m, b is the y-intercept

A parallel line will have the same slope and a different y intercept

A perpendicular line has a slope = -1/m

But x = -4 is a line parallel to the y axis intercepting the x-axis at -4. So slope = ∞

Therefore here are equations for a parallel line and a perpendicular line

A parallel line will have the form x = k where k is a constant(positive or negative). So x = 10 is a line parallel to x = -4

A perpendicular line will be of the form y = 4 or y = -10 or whatever, i.e. without the x component. Such a line will be parallel to the x-axis so both lines are perpendicular

Regarding your questions

y = 4x + 3 has a slope of 4 and a y intersect of 3 so it will be a sloping line
x = 4 will be parallel, not perpendicular to x = -4

I have provided a graph which makes this explanation clearer. The dotted line is x = 4 and you can see it is parallel to x = -4