Posts tagged linear equations

immatyrantlizard:

I’m having an issue understanding how to work the following problems:

Write the equation of a line that passes through point (2,4) and is parallel to y= -3

Write the equation of a line that passes through point (-1,3) and is perpendicular to x=7

I was absent the days that this assignment was given and problems like these were discussed.

first of all, the equation of line passing through a point (a,b) and having slope m is 

y-b = m( x-a)

for first problem, the line is parallel to y= -3

parallel lines have equal slopes

so the slope of line that you have to find out is also the same as the slope of the line y = -3

slope of line y = -3 is 0, since it is a line parallel to x axis passing through 0,-3

so your line is y - 4 = 0( x-2)

or y = 4

for second one, (-1,3) and the line is perpendicular to x = 7

x = 7 is a vertical line passing through 7,0

a line perpendicular to it is parallel to x axis, and any line parallel to x axis has slope = 0

so your line is y - 3 = 0( x+1)

or y = 3