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1 : jj 145 ##DESCRIPTION
2 :     ## lh2-3_48a.pg.
3 :     ##ENDDESCRIPTION
4 :    
5 :     ##KEYWORDS('algebra', 'increasing and decreasing functions')
6 :    
7 :     DOCUMENT(); # This should be the first executable line in the problem.
8 :    
9 :     loadMacros(
10 :     "PG.pl",
11 :     "PGbasicmacros.pl",
12 :     "PGchoicemacros.pl",
13 :     "PGanswermacros.pl",
14 :     "PGauxiliaryFunctions.pl",
15 :     "PGgraphmacros.pl",
16 :     "extraAnswerEvaluators.pl"
17 :    
18 :     );
19 :    
20 :     TEXT(beginproblem());
21 :     $showPartialCorrectAnswers = 1;
22 :    
23 :     $a = random(1,5,1);
24 :     $b = random(-5,0,1);
25 :    
26 :     $graph = init_graph(-10,-10,10,10,'axes'=>[0,0],'grid'=>[20,20],'size'=>[200,200]);
27 :     $f = FEQ("abs(x-$a)+abs(x+$a)+$b for x in <-10,10> using color:green and weight:2");
28 :    
29 :     plot_functions($graph,$f);
30 :    
31 :     BEGIN_TEXT
32 :     $BR
33 :    
34 :     Consider the function whose graph is sketched:
35 :     $BR \{ image(insertGraph($graph), width=>200, height=>200) \} $BR
36 :     Find the intervals over which the function is increasing or decreasing. If the answer includes more than one interval write the intervals separated by
37 :     the "union" symbol, U. You may use "infinity" for \(\infty\) and "-infinity" for \(-\infty\). For example, you may write (-infinity, 5] for the interval \((-\infty,5]\) and (-infinity, 5]U(7,9) for \((-\infty,5]\cup (7,9)\).
38 :     $BR $BR
39 :     The interval over which the function is increasing: \{ans_rule(35) \}
40 :     $BR
41 :     The interval over which the function is decreasing: \{ans_rule(35) \}
42 :     $PAR
43 :     END_TEXT
44 :    
45 :     ANS(interval_cmp("($a,infty)"));
46 :     ANS(interval_cmp("(-infty,-$a)"));
47 :    
48 :    
49 :    
50 :     ENDDOCUMENT(); # This should be the last executable line in the problem.

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