diket barisan geometri dengan U1+U2=18 dan U3=24. tentukan r yg bisa tolong bantu ya, terima kasih

[tex]a + ar = 18 \\ a(1 + r) = 18 \\ a{r}^{2} = 24 \\ a = \frac{24}{ {r}^{2} } \\ \frac{24}{ {r}^{2} } (1 + r) = 18 \\ 18 {r}^{2} - 24r - 24 = 0 \\ 3 {r}^{2} - 4r - 4 = 0 \\3 {r}^{2} - 6r + 2r - 4 = 0 \\ 3r(r - 2) + 2(r - 2) = 0 \\ (3r + 2)(r - 2) = 0 \\ r = - \frac{2}{3} \\ r = 2[/tex]