Question

Jonathan has been on a diet since January 2013. So far, he has been losing weight at a steady rate. Bases on monthly weigh-ins, his weight, w, can be modeled by the function w=-3m+205 where m is the number of months after January 2013.
a) How much did Jonathan weight at the start of the diet?

b) How much weight has Jonathan been losing each month?

c) How many months did it take Jonathan to lose 45 pounds?

Answer 1

$a)\ \ \ w(m)=-3m+205\\\\m=0\ \ \ - at\ the\ start\ of\ the\ diet\\ \\w(0)=-3\cdot0+205=205\\ \\Ans.\ weigh\ at\ the\ start\ of\ the\ diet\ is\ 205\ pounds\\ \\b)\ \ \ w(m+1)=-3(m+1)+2015=-3m-3+205=-3m+202\\ \\w(m+1)-w(m)=-3m+202-(-3m+205)=\\ \\=-3m+202+3m-205=-3\\ \\Ans.\ Jonathan\ has\ each\ month\ 3\ been\ losing \\ \\ w(m)=205-45=160\ \ \ \Rightarrow\ \ \ -3m+205=160\ \ \ \Rightarrow\ \ \-3m=-45\\ \\m=15\\ \\Ans.\ 15\ month$