Question

if s10=55 and s9=45 find a10​

Answer 1

Answer:

Sn=n/2{2a+(n-1)d}

S10=10/2{2a+9d}

55=5{2a+9d}

11=2a+9d----------1

S9=9/2{2a+8d}

45x2=9{2a+8d}

10=2a+8d-----------2

eqn1 - eqn2

d=1

put the value of d in eqn1

a=1

t10=1+9x1

=1+9

=10