Find the 31st term of 405,397,389

165

Step-by-step explanation:

1) the difference of the given sequence is:

d=397-405=389-397= -8.

2) common view of the formula of the 'n' term is:

a(n)=a(1)+d*(n-1), where n - required number of the given sequence, a(1) - the 1st term of the given sequence, d - the difference calculated above.

3) if to perform substitution (n=31; a(1)=405 and d= -8) into the formula above, then:

a(31)=405-8*(31-1)=405-240=165.