Question

Sebuah persegi panjang mempunyai ukuran panjang (x+5) cm dan lebar (x-3) cm. Jika luas persegi panjang tsb 48 cm², maka keliling persegi panjang tsb adalah..... Jelaskan dgn caranya

Answer 1

L = 48
pl = 48
(x+5)(x-3) = 48
x² - 3x + 5x - 15 = 48
x² + 2x - 15 - 48 = 0
x² + 2x - 63 = 0
x² + 9x - 7x - 63 = 0
x(x+9) - 7(x+9) = 0
(x+9)(x-7) = 0
x = -9 atau x = 7 (memenuhi)

p = x+5
p = 7+5
p = 12 cm

l = x-3
l = 7-3
l = 4 cm

K = 2×(p+l)
K = 2×(12+4)
K = 2×16 cm
K = 32 cm

Answer 2

L = pxl
L = (x+5)(x-3)
48 = ( X²+2x -15)
0= x²+2x - 63
0= (x+9)(x-7)
x = -9 atau x=7

ambil x = 7
keliling = 2(p+l)
k= 2 (x+5+x-3)
k = 2(2x+2)
k= 2( 2.7 +2)
k = 2(14+2)
k= 2 . 16
k = 32 cm