Question

Diketahui panjang dan lebar persegi panjang dan lebar persegi panjang secara berturut-turut adalah (2x + 15) cm dan (3x + 5 ) cm.Jika keliling persegi panjang tersebut 80 cm , tentukan :
a.nilai x
b.ukuran panjang dan lebar,serta
c.luasnya !

Answer 1

Keliling = 2(P + L)
= 2(2x + 15 + 3x + 5)
= 2(5x + 20)
= 10x + 40

10x + 40 = 80
10x = 80 - 40
10x = 40
x = 40 / 10
x = 4

panjang = 2x + 15
= 2(4) + 15
= 8 + 15
= 23 cm

lebar = 3x + 5
= 3(4) + 5
= 12 + 5
= 17 cm

luas = 23 * 17
= 391 cm²

Answer 2

K = 2(p + l)

A :
80 = 2((2x + 15) + (3x + 5))
80 = 2(5x + 20)
80 = 10x + 40
80 - 40 = 10x
40 = 10x
4 = x
x = 4

B :
p = 2x + 15
p = 2(4) + 15
p = 8 + 15
p = 23 cm

l = 3x + 5
l = 3(4) + 5
l = 12 + 5
l = 17 cm

C:
L = pl
L = 23 x 17
L = 391 cm²