(X +10)cm (4x-3)cm jika keliling persegi panjang ABCD =84 cm tentukan luas persegi panjang ABCD tsb?

keliling = 2(p+l)
84 = 2{(x + 10) + (4x - 3)}
84 = 2(5x + 7)
84 = 10x + 14
70 = 10x
x = 7

panjang = 17 cm
lebar = 25 cm

luas = p x l
= 17 x 25
= 425 cm²

l = x + 10
p = 4x - 3

K = 84
2(p + l) = 84
p + l = 42
(x + 10) + (4x - 3) = 42
5x + 7 = 42
5x = 35
x = 7

p = (4x - 3) cm
p = (4(7) - 3) cm
p = 25 cm

l = (x + 10) cm
l = (7 + 10) cm
l = 17 cm

Luas = p.l
Luas = 25 cm . 17 cm
Luas = 425 cm²