Question

in the given Ap a3=15,s10=125,find d and a10​

Answer 1

Answer:

$clearly \: \\ a3 = 15 \\ a + (3 - 1)d = 15 \\ a + 2d = 15 \\ a = 15 - 2d\: \: \: \: .......(i) \\ s10 = \frac{10}{2} {2a + (10 - 1)d} \\ 5(2a + 9d) = 125 \: \: \: \: ........(ii) \\ now \: \\ 10a + 45d = 125 \\ 10(15 - 2d) + 45d = 125 \\ 150 - 20d + 45d = 125 \\ 25d = - 25 \\ d = - 1 \\ hence \: \\ a = 15 - 2( -1 ) \\ = 17$

Answer 2

Answer:

we get, d= -1

2a+9d=25

2a-9=25

2a = 34

a = 17

a=17 and d=-1

Now, a10= a+9d

= 17+(-9)

= 8

Hence, a10=8