Question

Segitiga ACB siku-siku di C.Jika BD=(2x+1)cm,AD =x , CD =6cm .Tentukan panjang BD!gunakan Tehnik

Answer 1

CD² = AD . BD
6²    = x . (2x+1)
36   = 2x² + x
0 = 2x² + x - 36
0 = 2x² - 8x + 9x - 36
0 = 2x (x -4) + 9 (x - 4)
0 = (2x + 9) (x - 4)

kemungkinannya ada 2, yaitu :
2x + 9 = 0 => 2x = -9 => x = -4 1/2 (*nggk mungkin)
x - 4 = 0 => x = 4 (mungkin)

maka x = 4
BD = 2x + 1 = 8 + 1 = 9 cm