Question

in an ap is 5 + S7 is equal to 167 and S10 is equals to235 then find the AP where an denotes the sum of uts first n terms
​

Answer 1

Answer:

Step-by-step explanation:

S10=235

5(a+9d)=235

a+9d=47.......eq1

S5+S7=167

5/2(a+4d)+7/2(a+6d)=167

5a/2+10d+7a/2+21d=167

31d+6a=167.......eq2

On solving eq 1 and 2

a=2

d=5

Sn=n/2[a+(n-1)d]

Sn=n/2[2+(n-1)(5)]

Sn=n/2(2+5n-5)

Sn=n/2(5n-3)