Question

Să se rezolve ecuația (n+1)!+5n!-40(n-1)!=0

Answer 1

(n+1)!+5n!-40(n-1)!=0

(n-1)! [n(n+1)+5n-40)=0; n≥1

(n-1)!≠0

=> n(n+1)+5n-40)=0

n²+n+5n-40=0

n²+6n-40=0

Δ=36+160=196

n1=(-6+14)/2=4

n2=(-6-14)/2=-10, nu convine

=> n=4