Jika titik(a,3) dan (3,5a) bergradien 7 ,a=

misalkan A(a, 3) dan B(3, 5a) maka 
M = (y₂ - y₁) / (x₂ - x₁)
7 = (5a - 3) / (3 - a)
7(3 - a) = 5a - 3
21 - 7a = 5a - 3
21 + 3 = 5a + 7a
       24 = 12a
      12a = 24
          a = 2