Posted by Watermelon on Wednesday, November 30, 2011 at 11:25pm.
a+8d = 4+5p
d = 5, so
a+40 = 4+5p
I assume you mean the sum of the *first* 4 terms is 7p-10,so
4/2 (a + a+3d) = 7p-10
2(2a+15) = 7p-10
4a + 30 = 7p-10
So, rearranging things a bit, we have
a - 5p = -36
4a - 7p = -40
13p = 104
p = 8
a = 4
so, the sequence is
4,9,14,19,24,29,34,39,44,49
9th term is 4+40 = 44
sum of 1st 4 terms is 46 = 56-10