• {4, 7, 12, 19, … }
has 1st differences
7 - 4 = 3
12 - 7 = 5
19 - 12 = 7
and 2nd differences
5 - 3 = 2
7 - 5 = 2
• {-1, 2, 7, 14, …}
1st differences:
2 - (-1) = 3
7 - 2 = 5
14 - 7 = 7
2nd differences:
5 - 3 = 2
7 - 5 = 2
• {-2, -8, -18, -32, …}
1st differences:
-8 - (-2) = -6
-18 - (-8) = -10
-32 - (-18) = -14
2nd differences:
-10 - (-6) = -4
-14 - (-10) = -4
Answer:
Hello,
Step-by-step explanation:
I am going to explain the method with the 1th:
[tex]\begin{array}{ccccc}n & u_n&u_{n+1}-u_{n}&u_{n+2}-2u_{n+1}+u_{n}&v_{n}\\1&4&&6\\2&7&3&9\\3&12&5&2&14\\4&19&7&2&21\\...&&&\\\end{array}\\\boxed{u_{n+2}=2u_{n+1}-u_{n}+2}\\[/tex]
[tex]Let\ say\\v_{n}=u_{n}+2\\v_{n+2}=u_{n+2}+2=(2u_{n+1}-u_{n}+2)+2=2(v_{n+1}-2)-(v{n}-2)+4\\v_{n+2}=2v_{n+1}-v{n}+2\ (1)\\v_{n+3}=2v_{n+2}-v{n+1}+2\ (2)\\(2)-(1)==> \boxed{v_{n+3}=3v_{n+2}-3v_{n+1}+v_n}\\[/tex]
[tex]Caracteristic\ equation:\\P(r)=r^3-3r^2+3r-1=0\\P(r)=(r-1)^3\\v_n=\alpha+\beta*n+\gamma*n^2\\v_1=6 ==> \alpha+\beta*1+\gamma*1=6\\u_2=9 ==> \alpha+\beta*2+\gamma*4=9\\u_3=14 ==> \alpha+\beta*3+\gamma*9=14\\[/tex]
[tex]\begin{bmatrix}1&1&1\\1&2&4\\1&3&9\end{bmatrix}*\begin{bmatrix}\alpha\\\beta\\\gamma\end{bmatrix}=\begin{bmatrix}6\\9\\14 \end{bmatrix}\\\\\\\begin{bmatrix}1&1&1&6\\1&2&4&9\\1&3&9&14\end{bmatrix}\\\\\\\begin{bmatrix}1&1&1&6\\0&2&3&3\\0&2&8&8\end{bmatrix}\\\\\\\begin{bmatrix}1&1&1&6\\0&1&3&3\\0&1&4&4\end{bmatrix}\\\\[/tex]
[tex]\begin{bmatrix}1&1&1&6\\0&1&3&3\\0&0&1&1\end{bmatrix}\\\\\\\begin{bmatrix}1&1&1&6\\0&1&0&0\\0&0&1&1\end{bmatrix}\\\\\\\begin{bmatrix}1&0&0&5\\0&1&0&0\\0&0&1&1\end{bmatrix}\\[/tex]
[tex]\alpha=5\\\beta=0\\\gamma=1\\\boxed{v_n=5+0*n+1*n^2}\\\boxed{u_n=5+0*n+1*n^2-2}\\\begin{array}{ccccc}n & u_n\\1&5+1-2=4\\2&5+4-2=7\\3&5+9-2=12\\4&5+16-2=19\\...&...\\\end{array}\\[/tex]
