# quiz 3 - to A(t then(a find a differential equation and an...

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Fall 2008 Math 285 Quiz 3: Sep 24 Name: (J.,\,S!.l:JY:: ~~_ If you cannot complete a problem (perhaps because you forgot a formula) but you think you know how, please describe. Correct methods will receive partial credits. (\JDD.- K~ L j) -:: X: L ~ -+ L rx 'J . ~ht>< ( 'X 1 oJ )1' X ' 'X: t J ~~ 3 )c 1. S Q l\ l')(\;: ')( 3 \" C _ /\ f L ..J "\ l V- - I' -r ;;X L. 2. Initially 100 milligrams of a radioactive substance was present. After 6 hours the mass had decreased by 3%. We denote the amount of the substance present at time t by A(t). If the rate of decay is proportional
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Unformatted text preview: to A(t), then (a) find a differential equation and an initial condition that describe A(t). What is the sign of the constant of proportionality k in the d.e.? c1-f\ \f. . 1'\. c\ f\ A cl"t '" ~o ol t :: k .V\.itl~ k <.. OK ¥t ~-I:-f\ Vv"~ 1<>0 (b) the solution of the IVP in part (al is A(t) = 100ekt. Find the value of k. lU~' l~ 9r-~~U/\ Lk~ A(fc,') ~ (17 So Q \<:." ~ k ·1 7::: (00 e-t-e.. ~ 0, q-7. • I-...
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