Answer:
The first term is -6 and common difference is 3
Step-by-step explanation:
The nth term of an arithmetic progression is expressed as;
Tn = a + (n-1)d
T3 = a+2d
T4 = a + 3d
If the third term of an arithmetic sequence less than the fourth term by three
T3 = T4 - 3
a+2d = a+3d - 3
2d - 3d = -3
-d = -3
d = 3
Similarly;
T7 = a+6d
T5 = a+4d
If the seventh term is two times the fifth term, the;
T7 = 2T5
a+6d = 2(a+4d)
a+6d = 2a+8d
Since d = 3
a + 6(3) = 2a + 8(3)
a+18 = 2a + 24
a-2a = 24 - 18
-a = 6
a = -6
Hence the first term is -6 and common difference is 3
