persamaan garis yang melalui titik (1,-5) dan tegak lurus garis y= 2x+5 adalah

y = mx + c
y = 2x + 5

m1 = 2
m1×m2 = -1
2 m2 = -1
m2 = -1/2

y - y1 = m2 (x - x1)
y + 5 = -1/2(x - 1)
y + 5 = -1/2x + 1/2................. × 2
2y + 10 = -x + 1
x + 2y + 9 = 0
2y = -x - 9

y= 2x+5
Gradien(m) = 2
Karena tegak lurus maka:
m1.m2= -1
2.m2 = -1
m2 = -1/2
karena melalui titik (1,-5) maka:
y = mx + c
-5 = (-1/2)(1) + c
-5 = -1/2 + c
c = -5+ (1/2)
c = (-9/2)
Sehingga:
Persamaan garisnya:
y = (-1/2)x + (-9/2)
y = (-1/2)x - (9/2)

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