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 February 17th, 2018, 07:11 PM #11 Global Moderator   Joined: Dec 2006 Posts: 20,373 Thanks: 2010 Squaring gives $x^2 + 4x + 4 = x^2 + 14x + 49$, i.e. $10x + 45 = 0$, so $x = -9/2$. Why would that be wanted as an interval? Was the question mistyped? February 17th, 2018, 07:19 PM   #12
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 Originally Posted by skeeter No thanks. Went in January ... an expensive lesson in “hurry up & wait”
Sounds like somebody got their FastPass selections wrong. February 19th, 2018, 10:26 AM   #13
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 Originally Posted by shaharhada It's not my equation, but I want to understand the solution in the beginning part: but seriously folks... $|x+2| = |x+7|$ you can split this into 3 areas *$x < -7$ *$-7 \leq x \leq -2$ *$-2 < x$ In what way you get the (*) inequation?
It's derived from the definition of "absolute value". |x|= -x if x is negative, and |x|= x if x is non-negative. If x+ 7 is negative (so x< -7) |x+ 7|= -(x+7). If x+7 is non-negative (so $x\ge -7$) |x+7|= |x+7|. If x+ 2 is negative (so x< -2) |x+ 2|=-(x+ 2). If x+ 2 is non-negative (so $x\le -2$) |x+ 2|= x+ 2.

That's why romsek divided this into three regions, $x< -7$, $-7\le x< -2$, and $-2\le x$. In the first region x is less than both -7 and -2, in the second, x is larger than -7 but still less than -2, and in the third, x is greater than both -7 and -2. Tags calculus, equation, math or calculus, trigonometry or algebra, urgent 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 moazad655 Algebra 2 October 28th, 2014 01:27 PM junjie Algebra 12 November 4th, 2012 04:30 AM RolloJ Applied Math 1 October 23rd, 2008 10:58 AM balex Calculus 1 September 16th, 2007 01:35 PM junjie Complex Analysis 10 December 31st, 1969 04:00 PM

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