In an AP the the third and seventh terms are 14 and -2 respectively which term of the AP is -14
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Answer:n=10
Step-by-step explanation:
Given: third term,a3=14
and seventh term,a7=-2
also given that,an=-14
We know that,an=a+(n-1)d
therefore,
a3=a+(3-1)d
14=a+2d............(1)
and
a7=a+(7-1)d
-2=a+6d............(2)
On subtracting equation (1) from (2)...
We get,
= -2-14=a+6d-a+2d
= -16=4d
= d=-16/4
= d= -4
From the equation (1),we can write,
14=a+2d
14=a+2×(-4)
14=a+ (-8). { + × - =- }
a=14+8
a= 22
Let the nth term of this AP be -14
an=a+(n-1)d
-14=22+(n-1)(-4)
-14=22-4n+4
-14=26-4n
-4n=-14-26
= -40
n= -40/-4
n=10
Therefore,10th term of this arithmetic progression is -14
•: a10 = -14
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