SOLUTION: If the line passing through the points (a, 1) and (−18, 9) is parallel to the line passing through the points (−6, 7) and (a + 2, 1), what is the value of a?

Algebra ->  Points-lines-and-rays -> SOLUTION: If the line passing through the points (a, 1) and (−18, 9) is parallel to the line passing through the points (−6, 7) and (a + 2, 1), what is the value of a?      Log On


   

Question 1127520: If the line passing through the points
(a, 1) and (−18, 9)
is parallel to the line passing through the points
(−6, 7) and (a + 2, 1),
what is the value of a?
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
Parallel, the slopes equal

%289-1%29%2F%28-18-a%29=%281-7%29%2F%28a%2B2-%28-6%29%29
-
8%2F%28-a-18%29=-6%2F%28a%2B8%29
-8%2F%28a%2B18%29=-6%2F%28a%2B8%29
4%2F%28a%2B18%29=3%2F%28a%2B8%29
3%28a%2B18%29=4%28a%2B8%29
3a%2B54=4a%2B32
a=22