\(\left(x+3\right)\left(x+5\right)\left(x+7\right)\left(x+9\right)\)
\(=\left(x+3\right)\left(x+9\right)\left(x+5\right)\left(x+7\right)\)
\(=\left(x^2+12x+27\right)\left(x^2+12x+35\right)\)
\(=\left(x^2+12x+30-3\right)\left(x^2+12x+30+5\right)\)
\(=\left(x^2+12x+30\right)^2+2\left(x^2+12x+30\right)-15\)
Vậy số dư của phép chia là -15