Question 850797
You can work it out
Say, for now, that she bought it for {{{ x }}} dollars
Let {{{ V }}} = the value of the computer after {{{ n }}} years
After 1 year:
{{{ V = x - .1x }}}
After 2 years:
{{{ V = ( x - .1x ) - .1*( x - .1x ) }}}
I can factor out {{{ x - .1x }}}
{{{ V = ( x - .1x )*( 1 - .1 ) }}}
Factor out {{{ x }}}
{{{ V = x*( 1 - .1 )^2 }}}
After 3 years:
{{{ V =  ( x*( 1 - .1 )^2 ) - .1*( x*( 1 - .1 )^2 ) }}}
Factor out {{{ x*( 1 - .1 )^2 }}}
{{{ V = ( x*( 1 - .1 )^2 )*( 1 - .1 ) }}}
{{{ V = x*( 1 - .1 )^3 }}}
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This continues every year, so after {{{ n }}} years,
{{{ V = x*( 1 - .1 )^n }}}
This is a geometric sequence
{{{ x = 1250 }}}
{{{ n = 5 }}} 
{{{ V = 1250*( .9 )^5 }}}
{{{ V = 1250*.59049 }}}
{{{ V = 738.11 }}}
After 5 yrs, the computer is worth $738.11