dcastan2 wrote:

pike wrote:

f(4) = f(3) - 4

1) Sufficient, slot straights into above equation.

2)

f(6) = -1 = f(5) - 6

f(5) = 5 = f(4) - 5

f(4) = 10

Sufficient

D.

I don't understand what you mean slot straights into above equation. When I simplify the f(3) I get -1 and for f(6) I also get -1. Is that why both are sufficient? I don't understand why Statement 1 the f(3)=14. What I supposed to do something else?Hii.

See the question gives us the relation: \(f(n)=f(n-1)-n\) and the question asks the value of \(f(4)\).

As per the above relation, if we expand \(f(4)\), we get: \(f(4)=f(3)-4\)---------[a]

Now coming to the statements:

Statement 1 gives us direct \(f(3)\). We just have to put in equation [a].

Statement 2 gives us \(f(6)=-1\).

\(f(6)\) can be expanded as \(f(5)\)-6. Moreover \(f(5)\) can be expanded as \(f(4)-5\). Put this value of \(f(5)\) in the former one. It will become \(f(6)=f(4)-9\), which will gives the value of \(f(4)\) as 10.

Both are sufficient.

Hope that helps.

Yes, thank you! But we don't use the =14 anywhere? What's the purpose of it then?