#xin ctlhn, camon, 5sao
C = $\frac{12}{15}$ . $\frac{12}{15}$ . 4y² . $\frac{5}{9}$xy .$\frac{5}{9}$xy
C = $\frac{16}{25}$ . 4y² . ($\frac{5}{9}$ . $\frac{5}{9}$) . (x . x) . (y . y)
C = $\frac{64}{25}$ y² . $\frac{25}{81}$ x²y²
C = ($\frac{64}{25}$ . $\frac{25}{81}$) . (y² . y²) . x²
C = $\frac{64}{81}$ $y^{4}$ x²
Bậc: 6 (do 4 + 2 = 6)
@NT