Question

if sum of 3term 10th term is 9 and sum of 7th term and 15 term is 32 find a and d​

Answer 1

3rd term = a+2d.........(1)

10th term =a+9d........(2)

adding equation 1 and 2, we get:-

2a+11d

the sum of equation 1 and 2 is 9.

therefore

2a+11d=9................(3)

7th term = a+6d......(4)

15th term =a+14d....(5)

adding equation 4 and 5 we get:-

2a+20d

it is given that there sum is 32.

therefore

2a+20d=32..........(6)

subtracting equation 3 from equation 6,we get:-

9d=23

d=23/9

putting the value of d in equation 3 we get

2a + 11×23/9=9

2a+11×23=81

2a + 253 =81

2a=81-253

2a= 272

a=272/2

a=136

Answer 2

Refer the attachment.