Find an equation for the nth term of the arithmetic sequence.

-20, -16, -12, -8, .

Question

Find an equation for the nth term of the arithmetic sequence. 

-20, -16, -12, -8, .

anonymous · Answer

it is add 4

anonymous · Answer

-20, (-4) -16, (4) -12, (4) -8, (4) -4...

mathstudent55 · Answer

The first term is $a_1 = -20$

Each next term is 4 more than the previous term.

Term Number          Calculation                                 Term
1                             -20               = -20                    -20
2                             -20 + 4         =-20 + 4 * 1        -16
3                             -20 + 4 + 4  = -20 + 4 * 2        -12

anonymous · Answer

the 9th term will be positive 12

mathstudent55 · Answer

Low look at the pattern in the calculation column, right side.

anonymous · Answer

@Lethal sp would it be an = -20 + 4(n + 1)

mathstudent55 · Answer

n = 1 $a_n = a_1 =  -20$
n = 2 $a_n = a_2 = a_1 + 4(n - 1) = -20 + 4 = -16$
n = 3 $a_n = a_3 = a_1 + 4(n - 1) = -20 + 8 = -12$

The nth term is $a_n = -20 + 4(n - 1) $

agent0smith · Answer

@melacho a minor correction

 an = -20 + 4(n - 1)

anonymous · Answer

THANK YOU

wolf1728 · Answer

Couldn't the equation be written simpler such as:
an = -20 + n*4  ?
n = 1 -20 + 1*4 = -16
n = 2 -20 + 2*4 = -12

agent0smith · Answer

You could simplify it to an = -24+ 4n

wolf1728 · Answer

So then a0 = -24 and a1 = -20?