Question

if a third term of an arithmetic is 14 and the 8th term is -1, find the values of a1 and d of the sequence

Answer 1

How many steps from the 3rd term and the 8th term?

Answer 2

d=-5/2

Answer 3

a1 is 19

Answer 4

how do you do it

Answer 5

Just write the series dude a1, a1+d, a1+2d(3rd term=14) , a1+3d, ........a1+7d(8th term=-1)
Solve two equations for a1 and d
a1+2d=14
a1+7d=-1
Is it ok?????

Answer 6

I will try

Answer 7

Got it dude????????

Answer 8

not yet they do not want me to list them

Answer 9

Didnt got u

Answer 10

U have been given with the 3rd and 8th terms to find first term and arith.difference of the series right?????
Then use the formula u have for nth term a+(n-1)d
then substitute n value for ur terms given and eqaute to their vale
Solve the equations and get the result
This will the same thing i have done above

Answer 11

oh ok

Answer 12

sorry but I do not have a1 and d. and whats n

Answer 13

n is term given to u for the third term it is 3 and 8th term it is 8 and the expression in each equals to the value given to you

Answer 14

is it third=14 and 8th=-1

Answer 15

yeah exactly
a+(3-1)d=14
a+(8-1)d=-1

Answer 16

thats the method of two equation then sub 2 into 1 am I right

Answer 17

yeah i think you know to solve two simultaneous equations right????

Answer 18

yes I just did not get it at the first. I will let you know how I went

Answer 19

It appears like the delta between terms is -3. Assuming a1 is the first term of the series, it has to be 14+3+3 = 20.

Answer 20

I think I did it d=3 and a1=8

Answer 21

Atchyut are you there?

Answer 22

how does this work I did the second time and got d=5/3=1.6 and a1=10.8. both work so which one to use. help please

Answer 23

ok wait i will tell

Answer 24

you have the two equations
a1+2d=14
a1+7d=-1 right????

Answer 25

yes did
and the results are the ones written above

Answer 26

Subtract the second equation from first then a1 and a1 gets cancelled we will remain with
2d-7d=14-(-1)
-5d=15
and d= -15/5 =-3
and now substitute d=-3 in first equation a1-6=14 gives a1=20.
So a1 is 20 and d=-3
At first I thought something wrong and kept pth term equation inplace of 8 th term and so we get it like that

Answer 27

ok I will do it again

Answer 28

ok

Answer 29

how did you get -3 instead of 3

Answer 30

Once check my solution dude

Answer 31

think once first term is greater than the next terms.. how this is possible?????
It is possible only when the common difference is negative dude got it????

Answer 32

its geting more confusing because I did and got d=3 and a1=8 and tryed to do the sequence and it works but does not work for 8th term=-1