Question 53118: My question has come from a worksheet, not the actual text book. I am having trouble because my notes say I need to put it into point slope form, but I don't see how.
Here is my question:
Find the equation of a line through (-7,2) and perpendicular to y=2x.
Answer by funmath(2933)   (Show Source):
You can put this solution on YOUR website! Y=2x is already in slope intersept form (y=mx+b,m=slope,b=y-intersept)
In this case, the slope is 2 or 2/1.
The slope of a line that is perpendicular to that line would be its negative reciprocal (a fancy way of saying, "chage the sign and flip it upside down.") That means the slope of the line that we want to make is -1/2.
To do that we use m=-1/2 and the point (-7,2) in the point slope formula (y-y'=m(x-x'), m=slope, (x',y')=point)
y-2=-1/2(x-(-7))
y-2=-1/2(x+7)
2(y-2)=2(-1/2)(x+7)
2y-4=-1(x+7)
2y-4=-x-7
2y-4+4=-x-7+4
2y=-x-3
2y/2=-x/2-3/2
y=-1/2x-3/2 (Slope intercept form of a line)
If you were asked to write your equation in standard form (Ax+By=C)
2y=-x-3
x+2y=-3(Standard form of the same line)
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