Question

What is the 12th term of the arithmetic sequence where a1 = 5 and a6 = 20?

Answer 1

an=a1+d(n-1)
an=nth term
a1=first term
d=common differnce
n=which term

alrighty, a1=5

neat
an=5+d(n-1)
given a6=20
20=a6=5+d(6-1)
20=5+d(5)
20=5+5d
minus 5 both sides
15=5d
divide both sides by 5
3=d

so
an=5+3(n-1) is the formula for the nth term


12th term
a12=5+3(12-1)
a12=5+3(11)
a12=5+33
a12=38

the 12th term is 38