document.write( "Question 478755: Can someone please help solve this equation
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document.write( "6x(x-2)(3x+5)<0 \n" );
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Algebra.Com's Answer #328100 by Theo(13342)![]() ![]() You can put this solution on YOUR website! easy way to solve it is to graph it. \n" ); document.write( "that's kind of like cheating, but here goes. \n" ); document.write( " \n" ); document.write( "by looking at the graph you can see the regions that it's positive in and the regions that it's negative in. \n" ); document.write( "if you want to do it by formula, then you would want to find the 0 points of equation. \n" ); document.write( "set the equation equal to 0 to get: \n" ); document.write( "6x(x-2)(3x+5)=0 \n" ); document.write( "this equation will be 0 if: \n" ); document.write( "6x = 0 \n" ); document.write( "or: \n" ); document.write( "x-2 = 0 \n" ); document.write( "or: \n" ); document.write( "3x+5 = 0 \n" ); document.write( "solve for x in each of those equations and you get the overall equation being when: \n" ); document.write( "x = 0 \n" ); document.write( "x = 2 \n" ); document.write( "x = -5/3 \n" ); document.write( "look at the graph and you'll see that's where the graph crosses the x-axis. \n" ); document.write( "if you didn't have a graph to look at, you would simply know that the equation is equal to 0 when x is the values shown. \n" ); document.write( "the equation you are using is a continuous function. \n" ); document.write( "this means that there are no breaks in the line of the equation. \n" ); document.write( "it is smooth and continuous from end to end. \n" ); document.write( "this means that: \n" ); document.write( "before or after or in between the 0 points of the equation, if it's negative it will stay negative, and if it's positive it will stay positive. \n" ); document.write( "since you know the 0 points, just check each section before and after and between when x = 0 to see if the y value of the equation is negative or positive. \n" ); document.write( "pick a value for x and solve the equation using that value. \n" ); document.write( "----- \n" ); document.write( "assume x = -2 which is less than -5/3. \n" ); document.write( "when x = -2, the expression of 6x * (x-2) * (3x+5) = -12*(-4)*(-1) which will be negative because you have a minus times a minus times a minus. \n" ); document.write( "this means the equation is negative before the value of x = -5/3. \n" ); document.write( "----- \n" ); document.write( "assume x = -1 which is greater than -5/3 but less than 0. \n" ); document.write( "when x = -1, the expression of 6x * (x-2) * (3x+5) = -6*(-3)*2) = 36 which is a minus times a minus times a plus. \n" ); document.write( "this means that the equation is positive between the values of x = -5/3 and x = 0. \n" ); document.write( "----- \n" ); document.write( "assume x = 1 which is greater than x = 0 and less than x = 2. \n" ); document.write( "when x = 1, the expression of 6x * (x-2) * (3x+5) = 6*(-1)*(15) which is a plus times a minus times a plus. \n" ); document.write( "this means that the equation is negative between the values of x = 0 and x = 2. \n" ); document.write( "----- \n" ); document.write( "assume x = 3 which is greater than x = 2. \n" ); document.write( "when x = 3, the expression of 6x * (x-2) * (3x+5) = 18*1*14 which is a plus times a plus times a plus. \n" ); document.write( "this means that the equation is positive after the value of x = 2. \n" ); document.write( "----- \n" ); document.write( "put these all together and you get: \n" ); document.write( "when x < -5/3, the equation is negative. \n" ); document.write( "when x > -5/3 but < 0, the equation is positive \n" ); document.write( "when x > 0 but < 2, the equation is negative. \n" ); document.write( "when x > 2, the equation is positive. \n" ); document.write( "the question is to find when the equation is negative. \n" ); document.write( "that occurs when:\" \n" ); document.write( "x < -5/3 \n" ); document.write( "x > 0 but < 2 \n" ); document.write( "all other times the equation is either equal to 0 or greater than 0. \n" ); document.write( "this can be written as: \n" ); document.write( "x < -5/3 or 0 < x < 2 \n" ); document.write( "check the graph again to see if it concurs.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( " \n" ); document.write( " |