tolong dibantu ya kk'

Panjang BD = 9 cm - 4 cm
                    = 5 cm

AD = √BD x CD
      = √5 x 4
      = √20 cm

Kesebangunan

CD = 4 cm
BC = 9 cm
BC = CD + DB
DB = BC - CD
DB = 9 - 4
DB = 5 cm

AD² = CD x DB
AD² = 4 x 5 = 20
AD = √20