I think the answer should be E.
If i am correct let me know..so that i can shoot my logic..
Gmat Prep exam question
This topic has expert replies
Source: Beat The GMAT — Problem Solving |
-
simplythebest
- Junior | Next Rank: 30 Posts
- Posts: 22
- Joined: Mon Sep 18, 2006 10:17 am
-
thumpin_termis
- Senior | Next Rank: 100 Posts
- Posts: 60
- Joined: Fri Jun 01, 2007 11:02 pm
Another vote for e.
I find just plugging in numbers to something like this the most intuitive.
let a=1, and b=2
then, go through the answer choices and plug it in:
so if
f(x) = -3x (answer choice e)
then,
f(a) = f(1) = -3(1) = -3
f(b) = f(2) = -3(2) = -6
f(a+b) = f(1+2) = f(3) = -3(3) = -9
thus
f(a+b) = f(a) + f(b)
If you try this out on other answer choices, you'll see that it doesn't fit.
I find just plugging in numbers to something like this the most intuitive.
let a=1, and b=2
then, go through the answer choices and plug it in:
so if
f(x) = -3x (answer choice e)
then,
f(a) = f(1) = -3(1) = -3
f(b) = f(2) = -3(2) = -6
f(a+b) = f(1+2) = f(3) = -3(3) = -9
thus
f(a+b) = f(a) + f(b)
If you try this out on other answer choices, you'll see that it doesn't fit.
