MagpiesFreak7
New Member
- Joined
- Nov 13, 2012
- Messages
- 8
- Gender
- Male
- HSC
- 2013
-
Best of luck to the class of 2024 for their HSC exams. You got this! Let us know your thoughts on the HSC exams here -
YOU can help the next generation of students in the community! Share your trial papers and notes on our Notes & Resources page
Arithmetic Sequences HELP! (1 Viewer)
- Thread starter MagpiesFreak7
- Start date
MagpiesFreak7
New Member
- Joined
- Nov 13, 2012
- Messages
- 8
- Gender
- Male
- HSC
- 2013
Question 8 please
TheMathStudent
Member
- Joined
- Oct 19, 2011
- Messages
- 49
- Gender
- Undisclosed
- HSC
- 2004
- Uni Grad
- 2010
Keep in mind that the general equation for Sum is:
d) \\
S_n & =\frac{na+n^2 d -nd}{2} \\
S_n &=n^2 \frac{d}{2}+ n\frac{(a-d)}{2}\equiv n^2 - 3n \\
\therefore & \frac{d}{2}=1, \qquad \frac{(a-d)}{2}=-3
\end{align*}
)
I'll assume you can solve the last line with simultaneous equations
I'll assume you can solve the last line with simultaneous equations