My Math Forum  

Go Back   My Math Forum > High School Math Forum > Algebra

Algebra Pre-Algebra and Basic Algebra Math Forum


Reply
 
LinkBack Thread Tools Display Modes
August 11th, 2019, 07:39 AM   #1
Newbie
 
Joined: Aug 2019
From: Florida

Posts: 1
Thanks: 0

Which Expression Equals SAT Question

I have an SAT practice question stating: Which of the following expressions is equivalent to (-4x^3)^2/3?

The answer is 2x^2 * 3√2 (or ^2/3, I don't know how to indicate that specifically using keys but the 3 is inside the v of the square root symbol)

But my question is how I would multiply that expression to get the answer? Any math calculator or guide I consult seems to say that you can't multiply the expression, but it's clearly happening here.

Thank you very much!
SATboi is offline  
 
August 11th, 2019, 09:01 AM   #2
Global Moderator
 
Joined: Dec 2006

Posts: 21,015
Thanks: 2250

If x is real, $\left(-4x^3\right)\!^{2/3} = \left(-2^2\!\left(x^3\right)\right)\!^{2/3} = \left((-2)^{4/3}\right)\!x^2 = 2\!\left(2^{1/3}\right)\!x^2 = 2\sqrt[\large3]{2}x^2\!$.
skipjack is offline  
August 13th, 2019, 05:15 PM   #3
Senior Member
 
Joined: Oct 2013
From: New York, USA

Posts: 673
Thanks: 88

To show my work without using fractional exponents as much, take the square and then the cube root. The square is 16x^6. To simplify, write it as 2*8x^6. The cube root of 8 is the first part of skipjack's answer, the cube root of 2 is the second part of his answer, and the cube root of x^6 is x^2.
EvanJ is offline  
Reply

  My Math Forum > High School Math Forum > Algebra

Tags
equals, expression, question, sat



Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
short regular expression question Lobinho Computer Science 0 November 11th, 2015 12:06 PM
0.999... Equals 0.001... Less than 1 Anthony.R.Brown Number Theory 1 August 24th, 2013 08:56 AM
Question about rearranging an expression dtmowns Algebra 3 May 3rd, 2013 07:53 PM
Practical trig. question leads to a messy expression mglacy Trigonometry 1 June 3rd, 2012 03:18 PM
Volume Polynomial Expression Question Chee Algebra 1 November 3rd, 2011 05:56 PM





Copyright © 2019 My Math Forum. All rights reserved.