# Practice Problem (Intro to Discrete Math Class)

• January 15th 2009, 09:32 AM
Edbaseball17
Practice Problem (Intro to Discrete Math Class)
Hey Everyone,

Just so you know I am in an Intro to Discrete Math class so this stuff should be pretty simple to the rest of you, but I'm not very good at it. This is an example question that is up to me if i want to do it or not, the professor does not care. Any help would be appreciated.

Given that $A_n=5n+3$ for any $n>=1$, is it true that $A_n=5*A_{(n-1)} -3$?
• January 15th 2009, 09:37 AM
HallsofIvy
Quote:

Originally Posted by Edbaseball17
Hey Everyone,

Just so you know I am in an Intro to Discrete Math class so this stuff should be pretty simple to the rest of you, but I'm not very good at it. This is an example question that is up to me if i want to do it or not, the professor does not care. Any help would be appreciated.

Given that $A_n=5n+3$ for any $n>=1$, is it true that $A_n=5*A_(n-1) -3$?

I'm new to this so not sure how to make (n-1) all subscript, but it should be.

To make all of some expression a subscript enclose it in { }.
To calculate that, think of $A_n$ as a function A(n).
If $A_n= 5n+3$, then $A_{n-1}= 5(n-1)+ 3= 5n- 2$.
Put 5n+3 in place of $A_n$ and 5n- 2 in place of $A_{n-1}$ in that expression and see if it is true.
Is 5n+3= 5(5n-2)-3?
• January 15th 2009, 10:38 AM
Edbaseball17
Quote:

Originally Posted by HallsofIvy
To make all of some expression a subscript enclose it in { }.
To calculate that, think of $A_n$ as a function A(n).
If $A_n= 5n+3$, then $A_{n-1}= 5(n-1)+ 3= 5n- 2$.
Put 5n+3 in place of $A_n$ and 5n- 2 in place of $A_{n-1}$ in that expression and see if it is true.
Is 5n+3= 5(5n-2)-3?

ok so here is what I cam up with:

5n+3 = 5(n-2)-3 = 25n-10-3 = 25n-7