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<!DOCTYPE html>
<html data-require="math graphie expressions">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Midpoint of a segment</title>
<script src="../khan-exercise.js"></script>
<style>
.lcol { text-align:left; width:200px; display:inline-block; }
.rcol { text-align:left; width:auto; display:inline-block; }
</style>
</head>
<body>
<div class="exercise">
<div class="problems">
<div>
<div class="vars">
<var id="POINTS">randFromArray([ [ "A", "B", "C" ], [ "J", "K", "L" ], [ "C", "J", "T" ] ])</var>
<var id="SEG_1">POINTS[ 0 ] + POINTS[ 1 ]</var>
<var id="SEG_2">POINTS[ 1 ] + POINTS[ 2 ]</var>
<var id="SEG_TOTAL">POINTS[ 0 ] + POINTS[ 2 ]</var>
<div data-ensure="( COEF_1 !== COEF_2 || CONST_1 !== CONST_2 ) && ( TOTAL > 0 ) && ( CONST_2 !== 0 )">
<var id="X">randRange( 1, 9 )</var>
<var id="COEF_1">randRangeNonZero( 2, 9 )</var>
<var id="CONST_1">randRangeNonZero( -9, 9 )</var>
<var id="COEF_2">randRangeNonZero( 2, 9 )</var>
<var id="CONST_2">COEF_1 * X + CONST_1 - COEF_2 * X</var>
<var id="TOTAL">( COEF_1 * X + CONST_1 ) + ( COEF_2 * X + CONST_2 )</var>
</div>
</div>
<div class="problem">
<p><code><var>POINTS[ 1 ]</var></code> is the midpoint of <code>\overline{<var>SEG_TOTAL</var>}</code></p>
<div class="graphie" id="number-line">
init({
range: [ [ -1, 11 ], [ -1, 1 ] ]
});
line( [ 0, 0 ], [ 10, 0 ] );
style({ stroke: "#000", fill: "#000" });
graph.points = raphael.set();
graph.points.push( circle( [ 0, 0 ], 0.10 ) );
graph.points.push( circle( [ 5, 0 ], 0.10 ) );
graph.points.push( circle( [ 10, 0 ], 0.10 ) );
label( [ 0, 0 ], POINTS[ 0 ], "below" );
label( [ 5, 0 ], POINTS[ 1 ], "below" );
label( [ 10, 0 ], POINTS[ 2 ], "below" );
</div>
<p>
If:<br />
<span id="given1"><code>\qquad <var>SEG_1</var> = <var>COEF_1</var>x + <var>CONST_1</var></code></span> and<br />
<span id="given2"><code>\qquad <var>SEG_2</var> = <var>COEF_2</var>x + <var>CONST_2</var></code></span><br />
</p>
</div>
<p class="question">Find <code><var>SEG_TOTAL</var></code>.</p>
<div class="solution" data-forms="integer"><var>TOTAL</var></div>
<div class="hints">
<p>A midpoint divides a segment into two segments with equal lengths.</p>
<div>
<div class="graphie" data-update="number-line">
style({ stroke: BLUE, strokeWidth: 3 });
line( [ 0, 0 ], [ 5, 0 ] );
style({ stroke: GREEN, strokeWidth: 3 });
line( [ 5, 0 ], [ 10, 0 ] );
graph.points.toFront();
$( "#given1" ).css({ "color": BLUE });
$( "#given2" ).css({ "color": GREEN });
</div>
<p><code>\blue{<var>SEG_1</var>} = \green{<var>SEG_2</var>}</code></p>
</div>
<div>
<p>Substitute in the expressions that were given for each length:</p>
<p><code>\qquad \blue{<var>COEF_1</var>x + <var>CONST_1</var>} = \green{<var>COEF_2</var>x + <var>CONST_2</var>}</code></p>
</div>
<div>
<p>Solve for <code class="hint_pink">x</code>:</p>
<p><code class="hint_pink">\qquad <var>expr([ "*", COEF_1 - COEF_2, "x" ])</var> = <var>CONST_2 - CONST_1</var></code></p>
</div>
<p data-if="abs( COEF_1 - COEF_2 - 1 ) > 0.001" class="hint_pink"><code>\qquad x = <var>X</var></code></p>
<div>
<p>
Substitute <code class="hint_pink"><var>X</var></code> for <code class="hint_pink">x</code> in the expressions that were given for
<code class="hint_blue"><var>SEG_1</var></code> and <code class="hint_green"><var>SEG_2</var></code>:
</p>
<p>
<span class="lcol"><code class="hint_blue">\qquad <var>SEG_1</var> = <var>COEF_1</var>(\pink{<var>X</var>}) + <var>CONST_1</var></code></span>
<span class="rcol"><code class="hint_green">\qquad <var>SEG_2</var> = <var>COEF_2</var>(\pink{<var>X</var>}) + <var>CONST_2</var></code></span>
</p>
</div>
<p>
<span class="lcol"><code class="hint_blue">\qquad <var>SEG_1</var> = <var>COEF_1 * X</var> + <var>CONST_1</var></code></span>
<span class="rcol"><code class="hint_green">\qquad <var>SEG_2</var> = <var>COEF_2 * X</var> + <var>CONST_2</var></code></span>
</p>
<p>
<span class="lcol"><code class="hint_blue">\qquad <var>SEG_1</var> = <var>COEF_1 * X + CONST_1</var></code></span>
<span class="rcol"><code class="hint_green">\qquad <var>SEG_2</var> = <var>COEF_2 * X + CONST_2</var></code></span>
</p>
<div>
<p>To find the length <code><var>SEG_TOTAL</var></code>, add the lengths <code>\blue{<var>SEG_1</var>}</code> and <code>\green{<var>SEG_2</var>}</code>:</p>
<p><code>\qquad <var>SEG_TOTAL</var> = \blue{<var>SEG_1</var>} + \green{<var>SEG_2</var>}</code></p>
</div>
<p><code>\qquad <var>SEG_TOTAL</var> = \blue{<var>COEF_1 * X + CONST_1</var>} + \green{<var>COEF_2 * X + CONST_2</var>}</code></p>
<p><code>\qquad <var>SEG_TOTAL</var> = <var>TOTAL</var></code></p>
</div>
</div>
</div>
</div>
</body>
</html>
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