If you're experiencing a roadblock with one of the Manhattan Prep GMAT math strategy guides, help is here!
leovavassori
Forum Guests
 
Posts: 7
Joined: Sat Dec 03, 2011 9:14 am
 

If n is an integer and [-3(4n)] = [3(7n -3)], then n=

by leovavassori Fri Jan 20, 2012 12:47 pm

Hello there,

my question relates to the ADVANCED Quant book - Pg 167 -Question #10 In Action Problem Set. It reads:

NOTE: (x) = raised to whatever power is inside the brackets.

10) If n is an integer and [-3(4n)] = [3(7n -3)], then n=

[3(4n)] = [3(7n -3)]
4n = 7n - 3
n= 1

OK so I understand that because n is an integer multiplied by 4 the first 3 on the left side of the equation can only be positive. But what if that was not the case and the first 3 was raised to an odd power, could I still eliminate the bases on both side of equation? Or am I only allowed to do so when the bases are absolutely identical?

Cheers,

Leo
leovavassori
Forum Guests
 
Posts: 7
Joined: Sat Dec 03, 2011 9:14 am
 

Re: If n is an integer and [-3(4n)] = [3(7n -3)], then n=

by leovavassori Tue Jan 24, 2012 3:25 pm

Can anyone help please?
stud.jatt
Students
 
Posts: 21
Joined: Wed Aug 20, 2008 9:03 am
 

Re: If n is an integer and [-3(4n)] = [3(7n -3)], then n=

by stud.jatt Tue Jan 24, 2012 4:35 pm

No you can't. The reason is that you can only eliminate the base when both sides of the equation have the same base.

In the case where the Left Hand Side of the equation is raised to an odd power the base on the L.H.S is -3 while that on the R.H.S. is 3. And while -3 and 3 might look identical to you, THEY ARE NOT THE SAME NUMBER.

leovavassori Wrote:Hello there,

my question relates to the ADVANCED Quant book - Pg 167 -Question #10 In Action Problem Set. It reads:

NOTE: (x) = raised to whatever power is inside the brackets.

10) If n is an integer and [-3(4n)] = [3(7n -3)], then n=

[3(4n)] = [3(7n -3)]
4n = 7n - 3
n= 1

OK so I understand that because n is an integer multiplied by 4 the first 3 on the left side of the equation can only be positive. But what if that was not the case and the first 3 was raised to an odd power, could I still eliminate the bases on both side of equation? Or am I only allowed to do so when the bases are absolutely identical?

Cheers,

Leo
leovavassori
Forum Guests
 
Posts: 7
Joined: Sat Dec 03, 2011 9:14 am
 

Re: If n is an integer and [-3(4n)] = [3(7n -3)], then n=

by leovavassori Wed Jan 25, 2012 7:35 am

Cheers fella. I assumed as much but since I did not come across a case where one of the bases in the equation turned out to be negative I was a bit unsured.
tim
Course Students
 
Posts: 5665
Joined: Tue Sep 11, 2007 9:08 am
Location: Southwest Airlines, seat 21C
 

Re: If n is an integer and [-3(4n)] = [3(7n -3)], then n=

by tim Thu Feb 02, 2012 7:27 pm

cool. let us know if you have any more questions about this one..
Tim Sanders
Manhattan GMAT Instructor

Follow this link for some important tips to get the most out of your forum experience:
https://www.manhattanprep.com/gmat/forums/a-few-tips-t31405.html