Last visit was: 22 Dec 2024, 15:44 It is currently 22 Dec 2024, 15:44

Close

GRE Prep Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GRE score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel
Verbal Expert
Joined: 18 Apr 2015
Posts: 30475
Own Kudos [?]: 36820 [11]
Given Kudos: 26100
Send PM
Most Helpful Community Reply
Retired Moderator
Joined: 10 Apr 2015
Posts: 6218
Own Kudos [?]: 12234 [8]
Given Kudos: 136
Send PM
General Discussion
Verbal Expert
Joined: 18 Apr 2015
Posts: 30475
Own Kudos [?]: 36820 [0]
Given Kudos: 26100
Send PM
avatar
Intern
Intern
Joined: 23 Jun 2020
Posts: 30
Own Kudos [?]: 42 [2]
Given Kudos: 0
Send PM
Re: (x^y) * (x^2)=x^6 [#permalink]
2
So first we know that (x^y) * (x^2) = x^6
When we multiply two numbers that are expressed as x raised to some power, the result is x raised to the power of the sum of the two powers
So in our case 6 = y+2 which means y=4

Next:
(2z)^−2= 1/36

(2z)^-2 = 1/(2z)^2 = 1/(4z^2)

Now since 1/(4z^2) = 1/36 , we calculate z = 3

Lastly, we just compare 1/3 to 1/4 resulting in B as the right answer
Verbal Expert
Joined: 18 Apr 2015
Posts: 30475
Own Kudos [?]: 36820 [0]
Given Kudos: 26100
Send PM
Re: (x^y) * (x^2)=x^6 [#permalink]
Expert Reply
\((x^y) \times (x^2)=x^6\)

\(x^{y+2}=x^6\)

\(y=4\)

\((2z)^{-2} = \frac{1}{36}\)

\(\frac{1}{(2z)^2}=\frac{1}{36 }\)

\(\frac{1}{2^2 \times z^2}=6^2\)

Basically

\(4z^2=36\)

\(z^2=9\)

\(z=3\)

So y=4 and z=3

A is \(\frac{1}{4}\) and B is \(\frac{1}{3}\)

B is greater
avatar
Intern
Intern
Joined: 23 Jan 2020
Posts: 18
Own Kudos [?]: 31 [0]
Given Kudos: 0
Send PM
Re: (x^y) * (x^2)=x^6 [#permalink]
Carcass wrote:
\((x^y) \times (x^2)=x^6\)

\(x^{y+2}=x^6\)

\(y=4\)

\((2z)^{-2} = \frac{1}{36}\)

\(\frac{1}{(2z)^2}=\frac{1}{36 }\)

\(\frac{1}{2^2 \times z^2}=6^2\)

Basically

\(4z^2=36\)

\(z^2=9\)

\(z=3\)

So y=4 and z=3

A is \(\frac{1}{4}\) and B is \(\frac{1}{3}\)

B is greater


Could help explain why can't z also be -3?
Verbal Expert
Joined: 18 Apr 2015
Posts: 30475
Own Kudos [?]: 36820 [0]
Given Kudos: 26100
Send PM
Re: (x^y) * (x^2)=x^6 [#permalink]
Expert Reply
Attachment:
shot122.jpg
shot122.jpg [ 257.46 KiB | Viewed 8650 times ]


We have created the Quant math book for this purpose.

https://gre.myprepclub.com/forum/greprepcl ... -2609.html

Use it :wink:
avatar
Intern
Intern
Joined: 28 Jan 2020
Posts: 2
Own Kudos [?]: 3 [3]
Given Kudos: 0
Send PM
Re: (x^y) * (x^2)=x^6 [#permalink]
3
So, Z can be +3 or -3 right?
avatar
Intern
Intern
Joined: 23 Jan 2020
Posts: 18
Own Kudos [?]: 31 [2]
Given Kudos: 0
Send PM
Re: (x^y) * (x^2)=x^6 [#permalink]
2
Carcass wrote:
Attachment:
shot122.jpg


We have created the Quant math book for this purpose.

https://gre.myprepclub.com/forum/greprepcl ... -2609.html

Use it :wink:



I didn't know about this. Thanks a lot, it's very good.
But I am even more confused now, because as it says in this Quant book:

Carcass wrote:
This post is a part of [GRE MATH BOOK]


Exponential Equations:
When solving equations with even exponents, we must consider both positive and negative possibilities for the solutions.

For instance \(a^2=25\), the two possible solutions are \(5\) and \(-5\).


so in our example, z^2 = 9 ; z = 3 or - 3 ? right?
can you help shed some light here?

Originally posted by tpaillier on 30 Jun 2020, 13:14.
Last edited by tpaillier on 30 Jun 2020, 13:15, edited 1 time in total.
Verbal Expert
Joined: 18 Apr 2015
Posts: 30475
Own Kudos [?]: 36820 [0]
Given Kudos: 26100
Send PM
Re: (x^y) * (x^2)=x^6 [#permalink]
1
Expert Reply
Clear the way guys.

IF the variable is x^2= some value for instance x^2=25

x is equal to 5 AND minus 5

And the book is right. After all this is a universal math law.

Back to the question, I checked out the book from which I took it and YEs the book is wrong and @greenlighttest prep is RIGHT (as almost always) and the GRE Quant book I made is Correct . However, the book from the question comes from is WRONGG

\(z^2= 9\) ---------> z=+3 or -3

So in one case the answer is B and in the other case the answer is A

So the definite answer is D

Many Thanks
User avatar
GRE Prep Club Legend
GRE Prep Club Legend
Joined: 07 Jan 2021
Posts: 5090
Own Kudos [?]: 76 [0]
Given Kudos: 0
Send PM
Re: (x^y) * (x^2)=x^6 [#permalink]
Hello from the GRE Prep Club BumpBot!

Thanks to another GRE Prep Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
Prep Club for GRE Bot
Re: (x^y) * (x^2)=x^6 [#permalink]
Moderators:
GRE Instructor
88 posts
GRE Forum Moderator
37 posts
Moderator
1115 posts
GRE Instructor
234 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne