Question

Panjang diagonal-diangonal layang-layang ABCD ialah AC=8cm dan BD =(×+1)cm. Jika luas layang-layang tersebut 48cm, mka nilai BD adalah
A.5cm
B.7cm
C.12cm
D.13cm

Answer 1

Luas layang-layang 
d1.d2 / 2 = 48
8(x+1) / 2 = 48
4(x+1) = 48
4x+4 = 48
4x = 48-4
4x = 44
x = 44 / 4
x = 11

BD = (x+1) cm = (11+1) cm = c. 12 cm

Answer 2

Dik :
Dig AC = 8 cm
dig BD = x+1
L= 48 cm

maka :
L = (dig AC x dig BD ) / 2
48 = 8 x (x+1) / 2
48 x 2 = 8x + 8
96 = 8x + 8
8x  = 96 - 8
x   = 88/8
x  = 11

maka panjang BD = x + 1 = 11 + 1 = 12 cm (C)