How do you get from here.
http://quicklatex.com/cache3/ql_6f21...760b746_l3.png
to here?
http://quicklatex.com/cache3/ql_5970...25731d8_l3.png
Sorry about the links but site won't seem to accept the images as valid.
Thanks.
How do you get from here.
http://quicklatex.com/cache3/ql_6f21...760b746_l3.png
to here?
http://quicklatex.com/cache3/ql_5970...25731d8_l3.png
Sorry about the links but site won't seem to accept the images as valid.
Thanks.

Hello, AlyoshaKaz!
How do you get from here.
. . . . . . . . . . . . . . . . .r^{n-1} - 1
X(n) . = . ar^{n-1} + --------------- d
. . . . . . . . . . . . . . . . .. . r - 1
to here?
. . . . . . . . . . . . d . . . . . . . . . . . d
X(n) . = . (a + -----) r^{n-1} .- .------
. . . . . . . . . . .r - 1 . . . . . . . . . r - 1
Get a common denomiantor and add:
a(r - 1)r^{n-1} + (r^{n-1} - 1)d
---------------------------------------
. . . . . . . . . . r - 1
. . . . . a(r - 1)r^{n-1} + dr^{n-1} - d
. . = . --------------------------------------
. . . . . . . . . . . . . . . r - 1
. . . . .a(r - 1)r^{n-1} . . dr^{n-1} . . d
. . = . ------------------ + ----------- - ------
. . . . . . . . r - 1 . . . . . . . .r - 1 . . . r - 1
. . . . . . . . . . . . . dr^{n-1} . . d
. . = . ar^{n-1} + ----------- - -----
. . . . . . . . . . . . . . .r - 1 . . . r - 1
. . . . . . . . . d . . . . . . . . . .d
. . = . (a + -----)r^{n-1} - ------
. . . . . . . . r - 1 . . . . . . . .r - 1
I hope you could follow my steps . . .