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
April 13th, 2011, 12:09 PM   #1
Newbie
 
Joined: Apr 2011

Posts: 3
Thanks: 0

Help with radicals

I found this problem in a math book:

?(y) + 2 = ?(y + 16)

The answer in the back says that y = 9, and it works when you substitute it back in the equation, but I can't figure out how to solve it.
jonquil is offline  
 
April 13th, 2011, 12:32 PM   #2
Global Moderator
 
greg1313's Avatar
 
Joined: Oct 2008
From: London, Ontario, Canada - The Forest City

Posts: 7,571
Thanks: 931

Math Focus: Elementary mathematics and beyond
Re: Help with radicals

Square both sides and you'll be left with a single radical. Isolate the radical on one side of the equation and square both sides again, then solve for y.
greg1313 is offline  
April 13th, 2011, 01:03 PM   #3
Newbie
 
Joined: Apr 2011

Posts: 3
Thanks: 0

Re: Help with radicals

When I square both sides, don't I get

y + 4 = y +16 ?
jonquil is offline  
April 13th, 2011, 01:10 PM   #4
Senior Member
 
MarkFL's Avatar
 
Joined: Jul 2010
From: St. Augustine, FL., U.S.A.'s oldest city

Posts: 12,155
Thanks: 462

Math Focus: Calculus/ODEs
Re: Help with radicals

No, let's start with the original:



Square both sides:





Subtract y + 4 from both sides:



Divide through by 4:



Square both sides:



MarkFL is offline  
April 13th, 2011, 01:14 PM   #5
Newbie
 
Joined: Apr 2011

Posts: 3
Thanks: 0

Re: Help with radicals

Got it! No wonder I couldn't make it work. Thanks so much.
jonquil is offline  
April 13th, 2011, 01:19 PM   #6
Senior Member
 
MarkFL's Avatar
 
Joined: Jul 2010
From: St. Augustine, FL., U.S.A.'s oldest city

Posts: 12,155
Thanks: 462

Math Focus: Calculus/ODEs
Re: Help with radicals

You're welcome, and welcome to the forum!
MarkFL is offline  
April 13th, 2011, 03:40 PM   #7
Senior Member
 
Joined: Apr 2007

Posts: 2,140
Thanks: 0

?y + 2 = ?(y + 16)
(?y + 2) = ?(y + 16)
y + 4?y + 4 = y + 16
4?y = 16 - 4 = 12
?y = 12/4 = 3
?y = 3
? y = 9
johnny is offline  
Reply

  My Math Forum > High School Math Forum > Algebra

Tags
radicals



Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
I need help with radicals!! khales_m_j Algebra 1 January 13th, 2014 09:17 PM
Converting radicals to mixed radicals with fractions ohaider Algebra 6 February 6th, 2012 07:13 PM
More Radicals! SoupOrHero Algebra 2 February 19th, 2011 12:26 PM
Radicals SoupOrHero Algebra 2 February 14th, 2011 05:06 AM
Radicals jrobbo Algebra 7 February 10th, 2011 04:13 AM





Copyright © 2017 My Math Forum. All rights reserved.