Question

In a Ap a3 = 15 , S10 = 125 , find d and a10.​

Answer 1

d= -1

a10= 8

Step-by-step explanation:

It is given that, a3=15 ,S10=125

We can write a + 2d = 15 ----(1)

10/2[2a + 9d ] = 125

⇒5[2a + 9d ] = 125

⇒2a + 9d = 25 ----(2)

(1)*2 ⇒ 2a + 4d = 30 ---(3)

(2) - (3) ⇒

5d = -5

d = -1

eq (1) ⇒ a + 2d = 15

a + -1*2 = 15

a = 15 + 2 = 17

To find a10

a10 = a + 9d = 17 + 9*-1 = 17 - 9 = 8

hope it helps you...✌

Answer 2

a3 =15, S10 =125

a3=a+(3−1)d

15=a+2d

a=15−2d

s10 = 2/10 [2a+(10−1)d]

125=5[2a+9d]

25=2a+9d

25=2(15−2d)+9d

25=30−4d+9d

5d=−5

d=−1

a=15−2×(−1)

a=17

a10=a+(10−1)(−1)

a10 =17−9

a10 =26

HOPE IT HELPS YOU MATE....✌️