SOLUTION: Find y if the line through (9,3) and (-7,y) has a slope of -3/13

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Question 1101065: Find y if the line through (9,3) and (-7,y) has a slope of -3/13
Found 2 solutions by josmiceli, ikleyn:
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
slope = [ change in y ] / [ change in x ]
+%28+y+-+3+%29+%2F+%28+-7+-+9+%29+=+-3%2F13+
+%28+y+-+3+%29+%2F+%28-16%29+=+-3%2F13+
Multiply both sides by +-13%2A16+=+-208+
+13%2A%28+y+-+3+%29+=+3%2A16+
+13y+-+39+=+48+
+13y+=+87+
+y+=+87%2F13+
-------------------
check:
+%28+y+-+3+%29+%2F+%28-16%29+=+-3%2F13+
+%28+87%2F13+-+39%2F13+%29+%2F+%28-16%29+=+-3%2F13+
+48%2F13+=+%28+16%2A3+%29%2F13+
+48%2F13+=+48%2F13+
OK

Answer by ikleyn(52781) About Me  (Show Source):
You can put this solution on YOUR website!
The slope of a straight line passing through two given points  (x%5B1%5D,y%5B1%5D)  and  (x%5B2%5D,y%5B2%5D)  is:

m = %28y%5B2%5D-y%5B1%5D%29%2F%28x%5B2%5D-x%5B1%5D%29.


Substitute the given data into this equation


-3%2F13 = %28y-3%29%2F%28-7-9%29.


Simplify and solve for "y":


-3%2F13 = %28y-3%29%2F%28-16%29,  or,  equivalently,  3%2F13 = %28y-3%29%2F16.


y - 3 = %283%2A16%29%2F13 = 48%2F13 = 39%2F13  ====>  y = 69%2F13 = 87%2F13.