Tentukan persamaan garis yang melalui pasangan – pasangan titik – titik berikut….. a. 𝐶 ( 4, −2) dan 𝐷 (−6, −12) b. 𝑃 (9, 0) dan 𝑄 ( 0, −11) c. 𝑀 (−15, 0 ) dan 𝑁 ( 0, −8 )

Jawaban : a. x – y = 6 b. 11x – 9y = 99 c. 8x + 15y = –120 Penjelasan : Persamaan garis yang melalui dua titik ( (x1, y1) dan (x2, y2) ) : (y – y1)/(y2 – y1)=(x –x1)/(x2 – x1) a. (x1, y1) = (–6, –12) dan (x2, y2) = (4, –2), maka : (y –(–12))/(–2 –(–12)) = (x –(–6))/(4 –(–6)) (y + 12)/(–2 + 12) = (x + 6)/(4 + 6) (y + 12)/10 = (x + 6)/10 y + 12 = x + 6 x – y = 12 – 6 x – y = 6 b. (x1, y1) = (0, –11) dan (x2, y2) = (9, 0), maka : (y –(–11))/(0 –(–11))=(x – 0)/(9–0) (y + 11)/(0 + 11) = x / 9 (y + 11) / 11 = x / 9 (y + 11)×9 = x (11) 9y + 99 = 11x 11x – 9y = 99 c. (x1, y1) = (–15, 0) dan (x2, y2) = (0, –8), maka : (y – 0)/(–8 – 0) = (x –(–15))/(0–(–15)) y / (–8) = (x + 15)/(0 + 15) y / (–8) = (x + 15)/15 15(y) = (x + 15)×(–8) 15y = –8x – 120 8x + 15y = –120