math
posted by lindsay .
The 9th term of an AP is 8 and the 4th term is 20. Find the first term and the common difference.

Let d be the difference between terms.
Let x be the first term.
The second term will be x + d.
The third term will be x + 2d.
Fourth term will be x + 3d.
But the fourth term is 20, so x + 3d = 20.
Continue this until you get the eighth term.
Write an equation about the eighth term.
Now you have two equations with two unknowns which you can solve to find both the first term and the difference.
Respond to this Question
Similar Questions

math
1) If the sum of the first n terms of a series is Sn where Sn=2n²n, (a)prove that the series is an AP, stating the first term and the common difference; (b)find the sum of the terms from the 3rd to the 12th inclusive 2) In an AP … 
Math
1) If the sum of the first n terms of a series is Sn where Sn=2n²n, (a)prove that the series is an AP, stating the first term and the common difference; (b)find the sum of the terms from the 3rd to the 12th inclusive 2) In an AP … 
MATH
Find the value of A + B if the A is the first term and B is the common difference of the sequence whose 4th term is 3 and 20th term is 35 
Utech
The 9th term of an Arithmetic Progression is 8 and the 4th term is 20. Find the first term and the common difference. 
Arithmetic Progression
In an AP the 6th term is half the 4th term and the 3rd term is 15. a. Find the fist term and the common difference. b. How many times are needed to give a sum that is less than 65? 
maths
The sum of the 3rd and 7th term of an A.P is 38 and the 9th term is 37..Find the first term and common difference 
math
if 4th term of an arithmetic progression is 3 times the 1st term nd 7th term exceeds twice the third term by 1. find the first term and common difference 
kumasi polytechnic
In A.P the difference between the 8th term and 4th term is 20,and the 8th term is one and half times the 4th term.Find the common difference, and the first term. 
ahisco
In an A.P the difference between the 8th term and 4th term is 20 and the 8th term is 1half timesthe fourth term. what is the common difference and the first term of the sequence 
additional mathematics
if the 2nd term and the 4th term of an arithmetic progression are 15 and 23 respectively, find the first term and the common difference