SOLUTION: my questions is : find the value of r so that the line through (8,r) and (4,5) has a slope of -4. a.11 b.-11 c.4 d.-4 thanks for your help!

Algebra ->  Radicals -> SOLUTION: my questions is : find the value of r so that the line through (8,r) and (4,5) has a slope of -4. a.11 b.-11 c.4 d.-4 thanks for your help!      Log On


   

Question 5435: my questions is :
find the value of r so that the line through (8,r) and (4,5) has a slope of -4.
a.11
b.-11
c.4
d.-4
thanks for your help!
Found 2 solutions by longjonsilver, amthomas6:
Answer by longjonsilver(2297) About Me  (Show Source):
You can put this solution on YOUR website!
gradient, m is defined as %28y%5B2%5D+-+y%5B1%5D%29%2F%28x%5B2%5D+-+x%5B1%5D%29.

Which is %28x%5B1%5D%29,y%5B1%5D? IT DOES NOT MATTER!!!! Just pick one and stick with that decision:

so, i shall do both versions to show you, you get the same answer:

so, either m = (r-5)/(8-4) = -4
(r-5)/4 = -4
r-5 = -16
r = -11

OR m = (5-r)/(4-8) = -4
(5-r)/-4 = -4
5-r = 16
-r = 11
r = -11

jon.

Answer by amthomas6(1) About Me  (Show Source):