Question

The sum of 10 term of an AP whose last term is 28,is 145.Find the first term and the common difference.​

Answer 1

Step-by-step explanation:

s10= 145

t10 = 28

a= ?

d=?

t10 = a+(10-1)d

28= a+ 9d

a= 28-9d ... (I)

again ,

S10 = 10 /2(2a+(10-1)d)

145=5(2a+9d)

145/5 = 2a+ 9d

29 =2(28-9d)+9d

29 =56 - 18d + 9d

29 -56=9d-18d

........... do after this ,

again,

put the value of d in equation 1 .. ok?

I hope I will understand