document.write( "Question 896495: Toni is solving this equation by completing the square.
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document.write( "ax^2 + bx + c = 0 (where a is greater than or equal to zero)\r
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document.write( "Step one: ax^2 + bx = -c
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document.write( "Step two: x^2 + b/ax=-c/a
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document.write( "Step 3: ?\r
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document.write( "A. x^2=-c/b - b/ax
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document.write( "B. x + b/a= c/ax
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document.write( "C. x^2 + b/ax + b/2a = -c/a +b/2a
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document.write( "D. x^2 + b/ax + (b/2a)^2 =-c/a + (b/2a)^2 \n" );
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Algebra.Com's Answer #543547 by Theo(13342)![]() ![]() You can put this solution on YOUR website! i believe your solution is option D.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "start with ax^2 + bx + c = 0\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "divide both sides by a to get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x^2 + (b/a)x + (c/a) = 0\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "subtract (c/a) from both sides to get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x^2 + (b/a)x = -(c/a)\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "now take half the coefficient of the x term and square it and add it to both sides of the equation to get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x^2 + (b/a)x + (b/2a)^2 = -(c/a) + (b/2a)^2\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "this is selection D which is your answer.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "what comes next though?\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x^2 + (b/a)x + (b/2a)^2 is a perfect square and can be factored to get you:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "(x + (b/2a)^2 = -(c/a) + (b/2a)^2\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "when you square (x + (b/2a))^2, you get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "(x + (b/2a) * (x + (b/2a) which is equal to:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x^2 + (b/2a)^2 + (b/2a)x + (b/2a)x which simplifies to:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x^2 + 2 * (b/2a)x + (b/2a)^2 which further simplifies to:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x^2 + (b/a)x + (b/2a)^2\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "it's easier to see this with numbers.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "assume your equation is 2x^2 + 8x + 8 = 0 and you want to factor it using the completing the square method.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "step 1:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "divide both sides of the equation by 2 to get;\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x^2 + 4x + 4 = 0\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "step 2:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "subtract 4 from both sides of the equation to get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x^2 + 4x = -4\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "take half the coefficient of the x term to get 2 and square it to get 4 and add it to both sides of the equation to get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x^2 + 4x + 4 = -4 + 4 *****\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "***** this is your selection D with numbers instead of letters.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "simplify this to get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x^2 + 4x + 4 = 0\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "now factor the equation on the left, which is a perfect square.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "you will get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "(x + 2)^2 = 0\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "now take the square root of both sides of this equation to get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x + 2 = 0\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "now solve for x to get x = -2\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "the equation has been factored and the solution is x = -2\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "the equation of 2x^2 + 8x + 8 = 0 will be true when x = -2\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "replace x with -2 and you get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "2*(-2)^2 + 8*(-2) + 8 = 0 which becomes:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "8 - 16 + 8 = 0 which becomes 0 = 0 which confirms the solution is correct.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "selection D is your next step.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "if you take any equation in the form of x^2 + (b/a)x = -(c/a) and you take half the coefficient of the x term and square it and then add it to both sides of the equation, you form the perfect square on the left side of the equation.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x^2 + (b/a)x + (b/2a)^2 is a perfect square because, when you factor it, you get a factor that, when squared, it equal to it.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x^2 + (b/a)x + (b/2a)^2 is equal to (x + (b/2a))^2\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "you do have to add (b/2a)^2 to both sides of the equation, however, in order to preserve the equality.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "another example that is not as clean, but is still accurate according to the method.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "your equation is 3x^2 + 15x - 32 = 0\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "you want to factor this using the completing thed square method.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "divide both sides of the equation by 3 to get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x^2 + (15/3)x - (32/3) = 0\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "add (32/3) to both sides of the equation to get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x^2 + (15/3)x = (32/3)\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "simplify to get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x^2 + 5x = (32/3)\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "take half the coefficient of the x term and square it and add it to both sides of the eqution to get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x^2 + 5/x + (5/2)^2 = (32/3) + (5/2)^2\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "the left side of the equation is now a perfect square and can be factored to get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "(x + (5/2))^2 = (32/3) + (5/2)^2\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "notice that the constant term in the factor is (5/2)\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "it's the same constant that you squared and then added to both sides of the eqaution.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "if you simplify (x + 5/2)^2, you get (x + (5/2)) * (x + (5/2)) is equal to:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x^2 + (5/x)^2 + (5/2)x + (5/2)x which simplifies to:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "x^2 + 5x + (5/2)^2\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "there's your perfect square again.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "here's a link that talks about how to factor using the completing the square method.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "http://www.purplemath.com/modules/solvquad3.htm\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "that link includes other methods as well which are worth going through if you are interested in learning more about how to factor quadratics.\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( " \n" ); document.write( " |