Cara menghitung titik L(6.1)terhadap titik p(-4,-5)

titik L (6,1) dan P(-4,-5)
misal persamaannya adalah ax + by = xy
a.6 + b.1 = 6.1
6a + b = 6 ....1
a(-4) + b(-5) =-4.-5
-4a - 5b = 20 ....2
eliminasi b dari persamaan 1 dan 2
6a + b = 6 |× 5| 6.5 a + 5b = 6.5
-4a - 5b = 20 |×1| -4a - 5b = 20
30a + 5b = 30
-4a -5b = 20
-------------------- +
26 a = 50
a = 50/26 = 25/13
substitusi a = 25/13 kepersamaan 2
-4a -5b = 20
-4(25/13) - 5b = 20
-100/13 -5b = 20
-5b = 20 + 100/13
-5b = (20.13 + 100)/ 13
-5b =( 260 + 100)/13
= 360/13
b = 360/13 : 5
= 72/13
sehingga diperoleh persamaan garis lurus
25/13 x + 72/13 y = 25/13.72/13
25x + 72y = 1800/13