Question

Помогите решить уравнение на N

Answer 1

$P_ncdot A_{n+3}^3=n!cdotfrac{(n+3)!}{(n+3-3)!}=n!cdotfrac{(n+3)!}{n!}=(n+3)!\(n+3)!=30(n+1)!\(n+1)!cdot(n+2)cdot(n+3)=30(n+1)!\(n+2)(n+3)=30\n^2+5n+6=30\n^2+5n-24=0\D=25+4cdot24=121=(11)^2\n_{1,2}=frac{-5pm11}{2}\n_1=-8;-;He;nogx\n_2=3\OTBET:;3$