The 8th and 20th terms of an arithmetic sequence are 20 and 56 respectively. What is the 1st term of the sequence.

If the 8th and 20th terms of an arithmetic sequence are 20 and 56 respectively, then the 1st term of the sequence is -1

The nth term of an arithmetic sequence is given by the formula:

The 8th term of the arithmetic sequence is 20

The 20th term of the arithmetic sequence is 56

Subtract equation (1) from equation (2)

12d  =  36

d  =  36/12

d  =  3

Substitute d = 3 into equation (1)

a  +  7d  =  20

a  +  7(3)  =  20

a  +  21  =  20

a   =  20  -  21

a  =  -1

The first term of the arithmetic sequence is -1

Learn more here: link

Step-by-step explanation:

step-by-step explanation:

in the absence of parentheses, i will have to make some assumptions:   i interpret your (3x+5/y^6)(4y^3/5)​ to mean:

3x + 5     4y^(3/5)       (3x + 5)(4)

* =

    y^6             1               y^(6-3/5)

if this is not what you expected, repost your question using parentheses to indicate whether you meant

4y^3

    or   4y^(3/5)

    5

the answer is d

step-by-step explanation: