Question 1174043
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            Reading the post by  @ewatrr may confuse you,  since it is  INCORRECT.


            THEREFORE,  I came to bring the correct solution and correct answer.



<pre>
  2y + ax = 10

   y = -{{{(a/2)x}}} + 5


       m = {{{-a/2}}}  = 1


        1 = -a/2 ,  a = -2.    <U>ANSWER</U>


<U>ANSWER</U>.  The value of "a" must be -2.
</pre>

Solved (correctly).