My Math Forum SHOW how you solve the equation?

 Elementary Math Fractions, Percentages, Word Problems, Equations, Inequations, Factorization, Expansion

 December 21st, 2016, 01:50 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, 01:52 AM #2 Member   Joined: Sep 2016 From: India Posts: 88 Thanks: 30 $(x+2)^2 = 36$ $x + 2 = ± \sqrt{36}$ $x = −2 ± 6$ $x = 4 \;or −8$ Thanks from Davil and astro511
December 21st, 2016, 01:54 AM   #3
Newbie

Joined: Dec 2016
From: Chicago

Posts: 2
Thanks: 0

Quote:
 Originally Posted by deesuwalka $(x+2)^2 = 36$ $x + 2 = ± \sqrt{36}$ $x = −2 ± 6$ $x = 4 \;or −8$
Thank you so much for quick reply

 December 21st, 2016, 04:32 AM #4 Math Team   Joined: Dec 2013 From: Colombia Posts: 7,309 Thanks: 2444 Math Focus: Mainly analysis and algebra \begin{align*} (x+2)^2 &= 36 \\ x^2 + 4x + 4 &= 36 \\ x^2 + 4x - 32 &= 0 \\ (x + 8 )(x-4) &= 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} x-4 &= 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 Thanks from Davil
 December 21st, 2016, 07:05 AM #5 Math Team   Joined: Jan 2015 From: Alabama Posts: 3,171 Thanks: 869 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. Thanks from Davil Last edited by skipjack; December 21st, 2016 at 02:49 PM.
 December 21st, 2016, 04:22 PM #6 Math Team   Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 12,448 Thanks: 832 OK; now let's see your stuff: (2x+3)^2=81 Thanks from Joppy and Davil
December 22nd, 2016, 06:28 PM   #7
Newbie

Joined: Dec 2016
From: Philippines

Posts: 2
Thanks: 3

Math Focus: Algebra
Quote:
 Originally Posted by Denis OK; now let's see your stuff: (2x+3)^2=81
x=3 or x=-6
Am I right?

 December 22nd, 2016, 06:44 PM #8 Math Team   Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 12,448 Thanks: 832 Yes!! Thanks from Joppy and Davil
December 23rd, 2016, 10:04 AM   #9
Senior Member

Joined: Apr 2014
From: Europa

Posts: 571
Thanks: 176

Quote:
 Originally Posted by Denis OK; now let's see your stuff: (2x+3)^2=81

$\displaystyle \it \color{blue} {(2x+3)^2 = 81\Leftrightarrow \sqrt{(2x+3)^2}=\sqrt{81}\Leftrightarrow |2x+3| = 9 \Leftrightarrow 2x+3 = \pm9\Leftrightarrow \\\;\\ \Leftrightarrow 2x+3\in\{-9,\ 9\}|_{-3} \Leftrightarrow 2x\in\{-12,\ 6\}|_{:2}\Leftrightarrow x\in\{-6, \ 3\}}$

 December 23rd, 2016, 10:07 AM #10 Math Team   Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 12,448 Thanks: 832 Aurel, that'll scare poor Davil away !

 Tags elementry, equation, math, show, solve

 Thread Tools Display Modes Linear Mode

 Similar Threads Thread Thread Starter Forum Replies Last Post Hams Probability and Statistics 1 February 18th, 2016 10:44 AM Yulia Algebra 4 April 12th, 2012 04:22 PM vita2012 Trigonometry 4 February 18th, 2012 09:13 AM xx3004 Algebra 11 December 27th, 2010 08:27 PM Yulia Linear Algebra 0 December 31st, 1969 04:00 PM

 Contact - Home - Forums - Cryptocurrency Forum - Top