document.write( "Question 135087: Hello,I was wondering if anyone could help me solve this equation? I'm having trouble with it.
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document.write( "x^2-3x=18 the directions are to solve the equation.\r
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document.write( "Thank you,
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document.write( "Mrs. Gibson \n" );
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Algebra.Com's Answer #98926 by algebrapro18(249)![]() ![]() ![]() You can put this solution on YOUR website! Well in order to solve a quadratic equation we first must have it in standard form. Standard form is ax^2+bx+c = 0 where a, b, and c are numbers. \r \n" ); document.write( "\n" ); document.write( "so putting the function into standard form you get: \r \n" ); document.write( "\n" ); document.write( "x^2-3x=18 \n" ); document.write( "x^2-3x-18=0 \r \n" ); document.write( "\n" ); document.write( "now we need to factor. The steps to factoring are: \n" ); document.write( "1) Multiply a times c \n" ); document.write( "2) See what factors of the number found in step one add to the b value \n" ); document.write( "3) break the function into a product of its factors \r \n" ); document.write( "\n" ); document.write( "In this example a = 1, b = -3, and c = -18. So a*c = -18. So we need to find the factors of -18 that add to -3. Well the factors of 18 are: \r \n" ); document.write( "\n" ); document.write( "1,-18 \n" ); document.write( "2,-9 \n" ); document.write( "3,-6 \r \n" ); document.write( "\n" ); document.write( "well -6+3 = -3 so those are the factors we wanted. \r \n" ); document.write( "\n" ); document.write( "So we now know that x^2-3x-18 can be written as (x-6)(x+3). This is now in factored form. \r \n" ); document.write( "\n" ); document.write( "Now we use the zero product property that states that you can set each one of those factors equal to zero and solve for x. \r \n" ); document.write( "\n" ); document.write( "x-6 = 0 \n" ); document.write( "x = 6 \r \n" ); document.write( "\n" ); document.write( "x+3 = 0 \n" ); document.write( "x = -3 \r \n" ); document.write( "\n" ); document.write( "so now we know that the solutions to the given equation are x = -3 and x = 6. \r \n" ); document.write( "\n" ); document.write( "Now to check our solutions: \r \n" ); document.write( "\n" ); document.write( "x^2-3x-18 = 0 \n" ); document.write( "(6)^2-3(6)-18=0 \n" ); document.write( "36 - 18 - 18 = 0 \n" ); document.write( "36 - 36 = 0 \n" ); document.write( "0 = 0 \r \n" ); document.write( "\n" ); document.write( "that solution checks out now lets check the other one \r \n" ); document.write( "\n" ); document.write( "x^2-3x-18 = 0 \n" ); document.write( "(-3)^2 - 3(-3) - 18 = 0 \n" ); document.write( "9 + 9 - 18 = 0 \n" ); document.write( "18 - 18 = 0 \n" ); document.write( "0 = 0 \r \n" ); document.write( "\n" ); document.write( "that solution also check's out. \n" ); document.write( " |