Question 104344: This is the question -
If (x,y) is a point on the line l of slop -2 and y intercept 2, y=-2x+2. (So,
for example, if (23,y) is a point on l, y= -2(23)+2= -44.) k is the line that is
perpendicular to l and contains the point (18,13). If (x,y) is a point on k,
express y in terms of x.
Thank you for any help that you can give me to understand this type of question.
Answer by ankor@dixie-net.com(22740)   (Show Source):
You can put this solution on YOUR website! If (x,y) is a point on the line l of slope -2 and y intercept 2, y = -2x + 2. (So, for example, if (23,y) is a point on l, y= -2(23)+2 = -44.)
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Assume you understand what they are saying here:
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k is the line that is perpendicular to l and contains the point (18,13). If (x,y) is a point on k, express y in terms of x.
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Perpendicular lines have slope relationship that can be expressed:
m1 * m2 = -1
Assume m1 = -2 (line l slope), and find m2 (k line slope which is perpendicular)
-2*m2 = -1
:
m2 = 
:m2 = + is the slope of k line
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We know the slope of k so find the y intercept (b), by using x,y of 18,13
Using the slope intercept form
y = mx + b
13 = 18 + b
13 = 9 + b
13 - 9 = b
b = +4
Our k equation is:
y = x + 4
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Confirm this, substitute 18 for x and see that y = 13
y = (18) = 4
y = 9 + 4
y = 13
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If you graphed these two lines, it would look like this:
purple line is l, y intercept at +2
green line is k, y intercept at +4
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Did this help you understand this stuff somewhat?
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