Question

The sum of the first 6 terms of an arithmetic progression is 120,if fourth term is 23, determine the common difference and first term.

Answer 1

Step-by-step explanation:

S6=120

S6=6/2[2a+(n-1)d]

=3(2a+5d)

120 =6a+15d --------(1)

a4=23 = a+3d

=> 23-3d=a--------(2)

substitute value of a in (1)

u get values of a and d