Question

The sixth yerm of an ap is -10 and tenth term is -26 find 15th term

Answer 1

Hi

Here is ur answer

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a6 = -10

a + (6-1)d = -10  

a + 5d = -10  ------------(1)

a10 = -26

a + (10-1 )d = -26

a + 9d = -26  --------------(2)

Solving both by using elimination method

We get,

d = - 16 / 4

d = -4

Then substitute d in equation 1 or 2

( I am substituting in 1)

a + 5 * -4 = -10

a + (-20) = -10

a  = -10 +20

a = 10

Therefore, to find a15

an = a + (n-1) d

a15 = 10 + ( 15-1 ) (-4)

     = 10 + 14 (-4)

     = 10 - 56

    = - 46

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Hope it helps U

Hope it helps U