Quadratic Modeling

[sunshinewalker65]

I have put information for a data set into Line 1 and Line 2 under STAT and CALC using QuadREG for the percents of murder cases solved in various years. Let f(t) represent the percent of murder cases solved for the year this is "t" YEARS SINCE 1980. NOTE: 1988 same as t=8

Data set as follows:

Year Percent of Cases Solved
1988 72
1990 67
1992 64
1994 62
1996 68
1998 73

For the Quadratic model for f (t) I get .3839t^2 - 3.753t + 72.357

Here are the questions.

1. Find f(20) and what does your result mean in terms of the situation?

2. Find the value(s) of t where f (t) = 69 (whole numbers) What does your result mean in terms of the situation?

3. Find the vertex = What does your result mean in terms of the situation?

 

[Deleted member 4993]

I have put information for a data set into Line 1 and Line 2 under STAT and CALC using QuadREG for the percents of murder cases solved in various years. Let f(t) represent the percent of murder cases solved for the year this is "t" YEARS SINCE 1980. NOTE: 1988 same as t=8

Data set as follows:

Year Percent of Cases Solved
1988 72
1990 67
1992 64
1994 62
1996 68
1998 73

For the Quadratic model for f (t) I get .3839t^2 - 3.753t + 72.357

Here are the questions.

1. Find f(20) and what does your result mean in terms of the situation?

2. Find the value(s) of t where f (t) = 69 (whole numbers) What does your result mean in terms of the situation?

3. Find the vertex = What does your result mean in terms of the situation?

These are straight forward questions - where are you stuck?

1. Asks you to find f(20) from your quadratic model (assuming it is correct f(t) = 0.3839t^2 - 3.753t + 72.357 ) - replace 't' by '20' and simplify to find the value. Where are you stuck?

2. 0.3839t^2 - 3.753t + 72.357 = 69 ? 0.3839t^2 - 3.753t + 3.357 = 0 ? this is a quadratic equation - what are the roots?

3. Quadratic equations represent a parabola ? what are the co-ordinates of the vertex whenthe equation of the parabola is y = ax[sup:3o05jtc0]2[/sup:3o05jtc0] + bx + c

Tell us where you are stuck.......