maths igcse p4/mj/(2007 & 2010)help needed?

[mak kings]

hi anybody there to help me i ve got problems in these questions and am unable to understand the answer at all:
for mj-p4-2007 http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Mathematics (0580)/0580_s07_qp_4.pdf
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Mathematics (0580)/0580_s07_ms_4.pdf
Q4(d)
Q7(d)
Q9(b)

for mj-p41-2010

Q2(b)
Q7(c)(i)
Q8(d)(iii)

:- your help will b a big one to me.!!plz help

 

[mak kings]

plus any note,explanationss or example answers on nth term ,,,its very confusing and im too much bad in it!!!

 

[mak kings]

thanx a bunch...this helpd me 2 sm exte