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document.write( " What we know about the line whose equation we are trying to find out: \n" );
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document.write( " - it goes through point (0, 0)
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document.write( " - it has a slope of -2
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document.write( " First, let's draw a diagram of the coordinate system with point (0, 0) plotted with a little blue dot: \n" );
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document.write( " Write this down: the formula for the equation, given point and intercept a, is \n" );
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document.write( " (see a paragraph below explaining why this formula is correct) \n" );
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document.write( " Given that a=-2, and , we have the equation of the line: \n" );
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document.write( " Explanation: Why did we use formula ? Explanation goes here. We are trying to find equation y=ax+b. The value of slope (a) is already given to us. We need to find b. If a point ( , ) lies on the line, it means that it satisfies the equation of the line. So, our equation holds for ( , ): Here, we know a, , and , and do not know b. It is easy to find out: . So, then, the equation of the line is: . \n" );
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document.write( " Here's the graph: \n" );
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