Question

if the point A (3,5) and B (4,4)lies on the graph of line ax+by=7 find the value of a

Answer 1

x = 3, y = 5
so, 3a + 5b = 7........... (i) equation

x = 1, y = 4 
a+4b = 7
a = 7-4b ..................(ii) equation

now put the value of (a) from 2nd equation in 1st equation

 ==>        3(7 - 4b) + 5b = 7
  
  ==>        21 - 12b + 5b = 7
             
  ==>        -12b + 5b = 7 - 21
             
  ==>         - 7b = - 14

  ==>          7b = 14
 
  ==>           b = 14/7
 
  ==>           b = 2


now put the value of (b) in 2nd equation
    
==>        a = 7 - 4(2)

==>        a = 7 - 8
 
==>        a = -1

so, the value of a is -1

Answer 2

hope it's help you .....