Confused.

[fourshorty]

Ok so I did a test at my college and I got everything correct except these three problems:

In exercises 5-7, use the given conditions to write an equation for each line in point-slope form and slope-intercept form.</p>


5. Passing through (2,1) and (-1, -8)


6. Passing through (-2,3) and perpendicular to the line whose equation is y = -1/2x - 4


7. Passing through (6,-4) and parallel to the line whose equation is x+2y = 5


I just want to know what the correct answer is with work, so I can check on what I did wrong thank you!

 

[Mathimatician]

Ok so I did a test at my college and I got everything correct except these three problems:

In exercises 5-7, use the given conditions to write an equation for each line in point-slope form and slope-intercept form.</p>


5. Passing through (2,1) and (-1, -8)


6. Passing through (-2,3) and perpendicular to the line whose equation is y = -1/2x - 4


7. Passing through (6,-4) and parallel to the line whose equation is x+2y = 5


I just want to know what the correct answer is with work, so I can check on what I did wrong thank you!

Point-slope form is like this: (y - h) = m (x - k) where (k,h) is any point on the line. m is the slope of the line. [Note: x is the independent variable for the line and y is its dependent variable]
Slope Intercept form is like this: y = mx + b where m is the slope of the line and b is the y value where the line touches the y axis. [Note: x is the independent variable for the line and y is its dependent variable]

For #5: you need to get the slope of the line you are trying to build. m = (-8 - 1)/(-1 - 2) = 3
then choose any point to build the Point Slope form of a line: y - 1 = 3 (x - 2) [I used point (2,1) and the slope of 3]
Now isolate y in in the above equation to get slope intercept form: y = 3x - 5.

for #6: Note that perpendicular lines have opposite-reciprocal slopes (opposite = change of sign; reciprocal = exchange numerator and denominator). keeping this in mind you are asked to build a line with slope of +2 because the given line for #6 is already in slope intercept form.
Now use (-2,3) and the slope +2 to build point slope form. y - 3 = 2(x - (-2))
Now isolate y to build slope intercept form.

for #7: Note that parallel lines have equal slopes.
The given line is in what is sometimes called 'standard form'. to get its slope you can isolate y and it will then be in slope intercept form. y = -x/2 +5/2, where you can see that the slope is, m = -1/2
Now use (6, -4) and m = -1/2 to build point slope form: y - (-4) = -1/2(x - 6)
Now isolate y to get slope intercept form.

 

[stapel]

In exercises 5-7, use the given conditions to write an equation for each line in point-slope form and slope-intercept form.</p>

5. Passing through (2,1) and (-1, -8)

6. Passing through (-2,3) and perpendicular to the line whose equation is y = -1/2x - 4

7. Passing through (6,-4) and parallel to the line whose equation is x+2y = 5

I just want to know what the correct answer is with work, so I can check on what I did wrong

A better way to learn where things went wrong is for you to show us your work. We have enough experience generally to be able to see what the problem is, and then provide specific helps.

Please be complete. Thank you!