5*(5*4!*(X+2)!-5*2*4!*(X+1)!)=36*(X!*5!*2)
5*(5!*(X+2)!-2*5!*(X+1)!)=36*(X!*5!*2)
5*((X+2)!-2*(X+1)!)=36*(X!*2)
5*(X+2)!-10*(X+1)!)=72*X!
5*(X+2)*(X+1)*X!-10*(X+1)*X!=72*X!
5*(X+2)*(X+1)-10*(X+1)=72
5*(X+2)*(X+1)-10*(X+1)-72=0
5(X+2)(x+1)-10(X+1))-72=0
解得:
x=