December 21st, 2016, 02:50 AM  #1 
Newbie Joined: Dec 2016 From: Chicago Posts: 2 Thanks: 0  SHOW how you solve the equation?
(x+2)^2=36

December 21st, 2016, 02:52 AM  #2 
Member Joined: Sep 2016 From: India Posts: 81 Thanks: 25 
$(x+2)^2 = 36 $ $x + 2 = ± \sqrt{36} $ $x = −2 ± 6 $ $x = 4 \;or −8 $ 
December 21st, 2016, 02:54 AM  #3 
Newbie Joined: Dec 2016 From: Chicago Posts: 2 Thanks: 0  
December 21st, 2016, 05:32 AM  #4 
Math Team Joined: Dec 2013 From: Colombia Posts: 6,448 Thanks: 2123 Math Focus: Mainly analysis and algebra 
$$\begin{align*} (x+2)^2 &= 36 \\ x^2 + 4x + 4 &= 36 \\ x^2 + 4x  32 &= 0 \\ (x + 8 )(x4) &= 0 \\ \end{align*}$$ And because the product is zero, at least one of the factors is zero. Thus $$\left. \begin{aligned} x+8 &= 0 \\ x &= 8 \end{aligned} \right\} \; \text{or} \; \left\{ \begin{aligned} x4 &= 0 \\ x &= 4 \end{aligned} \right.$$ ("Or" because it's not possible that both are true simultaneously). I'll leave you to demonstrate the factorisation of the cuadratic 
December 21st, 2016, 08:05 AM  #5 
Math Team Joined: Jan 2015 From: Alabama Posts: 2,279 Thanks: 570 
Deesuwalka's method is simpler though V8Archie's is more general. Notice that if you were given a value for x and asked to evaluate $\displaystyle (x+2)^2$ you would 1) add 2 to x 2) square Here, you are given the value, 36, and asked to find the x that will give that value. So you need to "back out": do the opposite instead of "add 2" you "subtract 2" and instead of "squaring" take the square root. And, of course, you have to reverse the order first take the square root, then add 2 as Deesuwalka did. Last edited by skipjack; December 21st, 2016 at 03:49 PM. 
December 21st, 2016, 05:22 PM  #6 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 8,467 Thanks: 575 
OK; now let's see your stuff: (2x+3)^2=81 
December 22nd, 2016, 07:28 PM  #7 
Newbie Joined: Dec 2016 From: Philippines Posts: 2 Thanks: 3 Math Focus: Algebra  
December 22nd, 2016, 07:44 PM  #8 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 8,467 Thanks: 575 
Yes!!

December 23rd, 2016, 11:04 AM  #9 
Senior Member Joined: Apr 2014 From: Europa Posts: 570 Thanks: 174  $\displaystyle \it \color{blue} {(2x+3)^2 = 81\Leftrightarrow \sqrt{(2x+3)^2}=\sqrt{81}\Leftrightarrow 2x+3 = 9 \Leftrightarrow 2x+3 = \pm9\Leftrightarrow \\\;\\ \Leftrightarrow 2x+3\in\{9,\ 9\}_{3} \Leftrightarrow 2x\in\{12,\ 6\}_{:2}\Leftrightarrow x\in\{6, \ 3\}}$ 
December 23rd, 2016, 11:07 AM  #10 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 8,467 Thanks: 575 
Aurel, that'll scare poor Davil away !


Tags 
elementry, equation, math, show, solve 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Anyone can show me how to solve this ?? :'(  Hams  Probability and Statistics  1  February 18th, 2016 11:44 AM 
Please would someone show me how to solve this equation?  Yulia  Algebra  4  April 12th, 2012 04:22 PM 
who can show me how to solve this trigonometric equation?  vita2012  Trigonometry  4  February 18th, 2012 10:13 AM 
Could you please show me a better way to solve this equation  xx3004  Algebra  11  December 27th, 2010 09:27 PM 
Please would someone show me how to solve this equation?  Yulia  Linear Algebra  0  January 1st, 1970 12:00 AM 