135. Solve the equation

$$
x(x+1)(x+2)(x+3)=5040
$$
Solution. By calculating the product of the first and fourth, and the second and third factors of the left side of the equation, we will have:

$$
\left(x^{2}+3 x\right)\left(x^{2}+3 x+2\right)=5040
$$

Let $x^{2}+3 x=y$, then $y^{2}+2 y-5040=0$ and $y_{1}=-72, y_{2}=70$. From this, $x^{2}+3 x=-72$ or $x^{2}+3 x=70$. In the first case, the equation has no real roots, the roots of the second equation are the numbers -10 and 7.

Answer: $x_{1}=-10, x_{2}=7$