Mixing
How to find the first term and common difference in AP?
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Given that $a_1,a_2,dots$ is an arithmetic sequence. Let $a_3=-2$, $a_{21}=70$.
Find the first term $a_1$ and common difference $d$.
The $n$th term of arithmetic sequence is
$$a_n=a_1+d(n-1).$$
Using the above formula how to find $a_1$ and $d$?
arithmetic
edited Jun 20 '18 at 11:37
David
2,21711131
asked Jun 20 '18 at 11:27
VernaVerna
62
$endgroup$
add a comment |
$begingroup$
Given that $a_1,a_2,dots$ is an arithmetic sequence. Let $a_3=-2$, $a_{21}=70$.
Find the first term $a_1$ and common difference $d$.
The $n$th term of arithmetic sequence is
$$a_n=a_1+d(n-1).$$
Using the above formula how to find $a_1$ and $d$?
arithmetic
edited Jun 20 '18 at 11:37
David
2,21711131
asked Jun 20 '18 at 11:27
VernaVerna
62
$endgroup$
$begingroup$
Welcome to MSE. It will be more likely that you will get an answer if you show us that you made an effort. Also please use MathJax for mathematical formula and notations: math.meta.stackexchange.com/questions/5020/… Also... en.wikipedia.org/wiki/Arithmetic_progression
$endgroup$
– Tony Hellmuth
Jun 20 '18 at 11:28
add a comment |
$begingroup$
Given that $a_1,a_2,dots$ is an arithmetic sequence. Let $a_3=-2$, $a_{21}=70$.
Find the first term $a_1$ and common difference $d$.
The $n$th term of arithmetic sequence is
$$a_n=a_1+d(n-1).$$
Using the above formula how to find $a_1$ and $d$?
arithmetic
edited Jun 20 '18 at 11:37
David
2,21711131
asked Jun 20 '18 at 11:27
VernaVerna
62
$endgroup$
Given that $a_1,a_2,dots$ is an arithmetic sequence. Let $a_3=-2$, $a_{21}=70$.
Find the first term $a_1$ and common difference $d$.
The $n$th term of arithmetic sequence is
$$a_n=a_1+d(n-1).$$
Using the above formula how to find $a_1$ and $d$?
arithmetic
arithmetic
edited Jun 20 '18 at 11:37
David
2,21711131
asked Jun 20 '18 at 11:27
VernaVerna
62
edited Jun 20 '18 at 11:37
David
2,21711131
asked Jun 20 '18 at 11:27
VernaVerna
62
edited Jun 20 '18 at 11:37
David
2,21711131
edited Jun 20 '18 at 11:37
David
2,21711131
edited Jun 20 '18 at 11:37
David
2,21711131
2,21711131
asked Jun 20 '18 at 11:27
VernaVerna
62
asked Jun 20 '18 at 11:27
VernaVerna
62
asked Jun 20 '18 at 11:27
VernaVerna
62
62
$begingroup$
Welcome to MSE. It will be more likely that you will get an answer if you show us that you made an effort. Also please use MathJax for mathematical formula and notations: math.meta.stackexchange.com/questions/5020/… Also... en.wikipedia.org/wiki/Arithmetic_progression
$endgroup$
– Tony Hellmuth
Jun 20 '18 at 11:28
add a comment |
$begingroup$
Welcome to MSE. It will be more likely that you will get an answer if you show us that you made an effort. Also please use MathJax for mathematical formula and notations: math.meta.stackexchange.com/questions/5020/… Also... en.wikipedia.org/wiki/Arithmetic_progression
$endgroup$
– Tony Hellmuth
Jun 20 '18 at 11:28
$begingroup$
Welcome to MSE. It will be more likely that you will get an answer if you show us that you made an effort. Also please use MathJax for mathematical formula and notations: math.meta.stackexchange.com/questions/5020/… Also... en.wikipedia.org/wiki/Arithmetic_progression
$endgroup$
– Tony Hellmuth
Jun 20 '18 at 11:28
$begingroup$
Welcome to MSE. It will be more likely that you will get an answer if you show us that you made an effort. Also please use MathJax for mathematical formula and notations: math.meta.stackexchange.com/questions/5020/… Also... en.wikipedia.org/wiki/Arithmetic_progression
$endgroup$
– Tony Hellmuth
Jun 20 '18 at 11:28
add a comment |
1 Answer
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$begingroup$
Though SE expects your effort, I give hint so that you can give your $50%$ effort.
Hint:
Given $$a_3 = a_1 + (3-1) d = -2 tag{1}$$ and $$a_{21} = a_1 + (21-1) d = 70 tag{2}$$.
So solving these two equation with two unknown $a_1$ and $d$, leads to answer??
answered Jun 20 '18 at 11:40
DavidDavid
2,21711131
$endgroup$
add a comment |
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1 Answer
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1 Answer
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active
oldest
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$begingroup$
Though SE expects your effort, I give hint so that you can give your $50%$ effort.
Hint:
Given $$a_3 = a_1 + (3-1) d = -2 tag{1}$$ and $$a_{21} = a_1 + (21-1) d = 70 tag{2}$$.
So solving these two equation with two unknown $a_1$ and $d$, leads to answer??
answered Jun 20 '18 at 11:40
DavidDavid
2,21711131
$endgroup$
add a comment |
$begingroup$
Though SE expects your effort, I give hint so that you can give your $50%$ effort.
Hint:
Given $$a_3 = a_1 + (3-1) d = -2 tag{1}$$ and $$a_{21} = a_1 + (21-1) d = 70 tag{2}$$.
So solving these two equation with two unknown $a_1$ and $d$, leads to answer??
answered Jun 20 '18 at 11:40
DavidDavid
2,21711131
$endgroup$
add a comment |
$begingroup$
Though SE expects your effort, I give hint so that you can give your $50%$ effort.
Hint:
Given $$a_3 = a_1 + (3-1) d = -2 tag{1}$$ and $$a_{21} = a_1 + (21-1) d = 70 tag{2}$$.
So solving these two equation with two unknown $a_1$ and $d$, leads to answer??
answered Jun 20 '18 at 11:40
DavidDavid
2,21711131
$endgroup$
Though SE expects your effort, I give hint so that you can give your $50%$ effort.
Hint:
Given $$a_3 = a_1 + (3-1) d = -2 tag{1}$$ and $$a_{21} = a_1 + (21-1) d = 70 tag{2}$$.
So solving these two equation with two unknown $a_1$ and $d$, leads to answer??
answered Jun 20 '18 at 11:40
DavidDavid
2,21711131
answered Jun 20 '18 at 11:40
DavidDavid
2,21711131
answered Jun 20 '18 at 11:40
DavidDavid
2,21711131
answered Jun 20 '18 at 11:40
DavidDavid
2,21711131
2,21711131
add a comment |
add a comment |
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$begingroup$
Welcome to MSE. It will be more likely that you will get an answer if you show us that you made an effort. Also please use MathJax for mathematical formula and notations: math.meta.stackexchange.com/questions/5020/… Also... en.wikipedia.org/wiki/Arithmetic_progression
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– Tony Hellmuth
Jun 20 '18 at 11:28