jika AG = (2x -1 ) cm,maka panjang AC

AB = x cm
BC = (x + 3) cm
CG = (x - 1) cm
AG = (2x - 1) cm

AG = √((AB)²+(BC)²+(CG)²)
(2x - 1)² = (x)² + (x + 3)² + (x - 1)²
4x² - 4x + 1 = x² + x² + 6x + 9 + x² - 2x + 1
4x² - 4x + 1 = 3x² + 4x + 10
x² - 8x - 9 = 0
(x - 9)(x + 1) = 0

x = 9 cm
*karna panjang tidak mungkin negatif*

AC² = AB² + BC²
AC² = (9)² + (9 + 3)²
AC² = 81 + 144
AC = √225
AC = 15 cm