suatu persegi panjang (3x+10) cm, dan lebarnya (x+10) cm. jika keliling persegi panjang tersebut 144 cm, maka panjang dan lebar persegi panjang adalah

K = 2(p + l) = 2(3x + 10 + x + 10) = 2(4x + 20) = 8x + 40
144 = 8x + 40
8x = 144 - 40 = 104
x = 104/8 = 13
p = 3x + 10 = 3.13 + 10 = 39 + 10 = 49 cm
l = x + 10 = 13 + 10 = 23 cm

K = 2(p +l)
144 = 2{(3x+10) + (x+10)}
144 = 2{4x + 20}
144 : 2 = 4x + 20
72 = 4x + 20
72 - 20 = 4x
52 = 4x
52 : 4 = x
13 = x
Panjang = 3x + 10
= 3 x 13 + 10
= 39 + 10
= 49 cm
Lebar = x + 10
= 13 + 10
= 23 cm.
Semoga membantu anda.