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 April 19th, 2018, 02:44 AM #1 Newbie   Joined: Mar 2018 From: Canada Posts: 14 Thanks: 0 equation with exponent Hi everyone, I just have a doubt when solving the following. Here is what I've done. 2x^2=18 x^2=18/2 x^2=9 x=sqrt9 x=3 My doubt is if the answer is only 3 or -3 is also an answer because of the square root. Thank you April 19th, 2018, 03:02 AM #2 Math Team   Joined: Jan 2015 From: Alabama Posts: 3,264 Thanks: 902 It's easy to check, isn't it? 3^2= 9, 2(9)= 18 so 3 is a solution. (-3)^2= 9, 2(9)= 18 so -3 is also a solution. Both 3 and -3 are solutions. April 19th, 2018, 03:04 AM   #3
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 Originally Posted by Country Boy It's easy to check, isn't it? 3^2= 9, 2(9)= 18 so 3 is a solution. (-3)^2= 9, 2(9)= 18 so -3 is also a solution. Both 3 and -3 are solutions.
thank you! I just wanted to make sure ! April 19th, 2018, 03:48 AM #4 Senior Member   Joined: Oct 2009 Posts: 850 Thanks: 327 Note though that $\sqrt{9} = 3$ and not $-3$. The square root is by definition always positive. However, the solutions to $x^2=9$ are both $3$ and $-3$. Crucial distinction! Thanks from Country Boy April 19th, 2018, 08:07 AM   #5
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 Originally Posted by Micrm@ss Note though that $\sqrt{9} = 3$ and not $-3$. The square root is by definition always positive. However, the solutions to $x^2=9$ are both $3$ and $-3$. Crucial distinction!
thanks. That actually clarifies a lot! April 20th, 2018, 11:09 AM #6 Math Team   Joined: Jan 2015 From: Alabama Posts: 3,264 Thanks: 902 That's why you need the "$\displaystyle \pm$" when you say that "the solution to $\displaystyle x^2= a$ is $\displaystyle x= \pm\sqrt{a}$". Tags equation, exponent Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post hhmathgeek Algebra 13 January 21st, 2016 07:16 PM The_Ys_Guy Algebra 3 May 1st, 2015 07:21 PM bml1105 Algebra 12 July 27th, 2014 11:40 AM windsurfer19 Algebra 3 December 2nd, 2013 12:15 PM Bencz Algebra 4 May 4th, 2013 04:14 PM

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