Question

find the common difference of an a.p whose first term is 5 and 11th term is -5

Answer 1

Hey friend...! here's your answer
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an =a + (n - 1) d
a11 = 5 + ( 11 - 1) d

a11 = - 5

So,

- 5 = 5 + ( 11 - 1 ) d
- 5 - 5 = 10d
-10 = 10d
d = -1

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#Hope its help

Answer 2

Here is your answer

Let the common difference of given AP be d and a be its first term
Here,
a=5
A/q- T11= -5
a+(11-1)d= -5
5+10d= -5
10d= -5 -5
10d= -10
d= -10/10
d= -1

So, common difference of the given AP is -1