Question

find the sum of first term of AP whose third term is -103 and 7th term is -63​

Answer 1

Answer:

-123

Step-by-step explanation:

a+2d=-103...(1)

a+6d=-63....(2)

from equation (1)and(2)

d=10

a=-123

now

we, know that

sum of n term of ap=n/2{2a+(n-1)d}

sum of 1st term=1/2{2×(-123)}

1/2×(-246)

=-123