Wednesday, October 21, 2015

`a_0 = 3, a_2 = 0, a_6 = 36` Find a quadratic model for the sequence with the indicated terms.

You need to remember what a quadratic model is, such that:


`a_n = f(n) = a*n^2 + b*n + c`


The problem provides the following information, such that:


`a_0 = 3 => f(0) = a*0^2 + b*0 + c => c = 3`


`a_2 = 0 => f(2) = a*2^2 + b*2 + c => 4a + 2b + c = 0`


`a_6 = 36 => f(6) = a*6^2 + b*6 + c => 36a + 6b + c = 36`


You need to replace 3 for c in the next two equations, such that:


`4a + 2b + 3 = 0 => 4a + 2b = -3`


`36a + 6b + 3 = 36 => 36a + 6b = 33 => 18a + 2b = 11`


Subtract the equation `4a + 2b = -3` from the equation `18a + 2b = 11` :


`18a + 2b - 4a - 2b = 11 + 3`


`14a = 14 => a = 1`


Replace 1 for a in equation `4a + 2b = -3` , such that:


`4 + 2b = -3 => 2b = -7 => b = -7/2`


Hence, the quadratic model for the given sequence is `a_n = n^2 - (7/2)*n + 3.`

No comments:

Post a Comment

How does the choice of details set the tone of the sermon?

Edwards is remembered for his choice of details, particularly in this classic sermon. His goal was not to tell people about his beliefs; he ...