document.write( "Question 468457: Does anyone have an idea of how quadratic equations can have the same solutions? \n" ); document.write( "
Algebra.Com's Answer #321445 by Theo(13342)    You can put this solution on YOUR website! They will have the same solution at the points where the graphs of each equation intersect each other. \n" ); document.write( "An example would be: \n" ); document.write( "x^2 + 5x + 3 \n" ); document.write( "-x^2 + 5x + 6 \n" ); document.write( "The graph of both of these equations is shown below: \n" ); document.write( " \n" ); document.write( "The graph of these equations show that they will intersect at 2 places. \n" ); document.write( "Those places would be the common solutions for both equations. \n" ); document.write( "To find the intersection points, set the equations equal to each other and solve. \n" ); document.write( "We start with: \n" ); document.write( "x^2 + 5x + 3 = -x^2 + 5x + 6 \n" ); document.write( "Add x^2 to both sides of this equation and subtract 5x from both sides of this equation and subtract 6 from both sides of this equation to get: \n" ); document.write( "2x^2 - 3 = 0 \n" ); document.write( "Add 3 to both sides of this equation to get: \n" ); document.write( "2x^2 = 3 \n" ); document.write( "divide both sides of this equation by 2 to get: \n" ); document.write( "x^2 = 3/2 \n" ); document.write( "Take the square root of both sides of this equation to get: \n" ); document.write( "x = +/- sqrt(3/2) \n" ); document.write( "The 2 equations should intersect at the same value of y when x = +/- sqrt(3/2). \n" ); document.write( "That would be a common solution for both graphs. \n" ); document.write( "Our 2 equations are: \n" ); document.write( "y1 = x^2 + 5x + 3 \n" ); document.write( "y2 = -x^2 + 5x + 6 \n" ); document.write( "When x = + sqrt(3/2), these equations become: \n" ); document.write( "y1 = 10.62372436 \n" ); document.write( "y2 = 10.62372436 \n" ); document.write( "x = + sqrt(3/2) is roughly located at x = 1.2 \n" ); document.write( "Look at the graph and you'll see that when x = 1.2, the 2 equations intersect at somewhere around y = 10.6. \n" ); document.write( "When x = - sqrt(3/2), these equations become: \n" ); document.write( "y1 = -1.623624357 \n" ); document.write( "y2 = -1.623724357 \n" ); document.write( "x = - sqrt(3/2) is roughly located at x = -1.2 \n" ); document.write( "Look at the graph and you'll see that when x = -1.2, the 2 equations intersect at somewhere around y = -1.6. \n" ); document.write( "If you want to see what the graph of those equations looks like from a more distant perspective, it is shown below: \n" ); document.write( "  |