SOLUTION: Find the value of k so that the line containing the points (−7,−7) and (3,k) is perpendicular to the line y=−1/4x+1.

Algebra ->  Linear-equations -> SOLUTION: Find the value of k so that the line containing the points (−7,−7) and (3,k) is perpendicular to the line y=−1/4x+1.       Log On


   

Question 720029: Find the value of k so that the line containing the points (−7,−7) and (3,k) is perpendicular to the line y=−1/4x+1.
Found 2 solutions by josmiceli, mananth:
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Any line perpendicular to the line
+y+=+mx+%2B+b+
has a slope = +-1%2Fm+
In this case the slope is +-1%2F4+, so
+m+=+%28-1%29%2F%28+-1%2F4%29+
+m+=+4+
Now I can use the point-slope formula
+%28+k+-%28-7%29+%29+%2F+%28+3+-%28-7%29+%29+=+4+
+%28+k+%2B+7+%29+%2F+%28+3+%2B+7+%29+=+4+
+k+%2B+7+=+4%2A10+
+k+=+40+-+7+
+k+=+33+

Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
Find the value of k so that the line containing the points (−7,−7) and (3,k) is perpendicular to the line y=−1/4x+1.
y= -(1/4)x +1
slope = -(1/4)
a line perpendicular to this line will have a slope of 4 ( negative reciprocal)
m= (y2-y1)/(x2-x1)
4 = (k-(-7))/(3-(-7))
4= (k+7)/10
k+7=40
k=33