Sebuah persegi panjang mempunyai ukuran panjang (3×-3)cm dan lebar (×+8) cm. Jika keliling persegi panjang 58 cm, luasnya adalah

K = 2(p+l)
58 = 2( (3x-3)+(x+8) )
58 = 2(4x+5)
58 = 8x+10
8x = 58-10
8x = 48
x = 6

p = 3x-3
= 3.(6)-3
= 18-3
= 15 cm

l = x+8
= 6+8
= 14 cm

L = p×l
= 15×14
= 210 cm²

Semoga Membantu

Kell = 2( p + l)
58 = 2((3x - 3) + (x + 8))
58 = 2(3x + x -3 + 8)
58 = 2( 4x + 5)
58 = 8x + 10
58 - 10 = 8x
48 = 8x
48/8 = x
6 = x

luas = p x l
p = 3x - 3
p = 3(6) - 3
p = 18 - 3
p = 15

l = x + 8
l = 6+ 8
l = 14

luas = p x l
15 x 14 = 210 cm2