document.write( "Question 548975: solve the equation by completeing the square:\r
\n" ); document.write( "\n" ); document.write( "7x^2+10x=-2
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Algebra.Com's Answer #357384 by mathie123(224)\"\" \"About 
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\"7x%5E2%2B10x=-2\"\r
\n" ); document.write( "\n" ); document.write( "We will first put everything on one side of the equation (as in most classes, students are most familiar with completely the square when it is in the form ax^2+bx+c\r
\n" ); document.write( "\n" ); document.write( "this gives us:
\n" ); document.write( "\"7x%5E2%2B10x%2B2=0\"
\n" ); document.write( "Now we need to make the constant in front of x^2 1, so we will factor out a 7 from our first two terms:
\n" ); document.write( "\"7%28x%5E2%2B10%2F7%2Ax%29%2B2=0\"
\n" ); document.write( "Now the rules for completing the square say we must take the constant in front of the x and square one half of this number and add and subtract this number. \r
\n" ); document.write( "\n" ); document.write( "So our constant is 10/7. One half of 10/7 is
\n" ); document.write( "10/7*1/2=10/14
\n" ); document.write( "and this squared is
\n" ); document.write( "(10/14)^2=(5/7)^2=25/49\r
\n" ); document.write( "\n" ); document.write( "So we will add and subtract this number (so essentially we are adding 0 to our equation, which does not change it).
\n" ); document.write( "\"7%28x%5E2%2B10%2F7%2Ax%2B25%2F49-25%2F49%29%2B2=0\"
\n" ); document.write( "We will now take our -25/49 out of the bracket (remembering to multiply it by 7 when we take it out). this leaves:
\n" ); document.write( "\"7%28x%5E2%2B10%2F7%2Ax%2B25%2F49%29%2B2-25%2F49%2A7=0\"\r
\n" ); document.write( "\n" ); document.write( "Almost there....
\n" ); document.write( "We will complete the square inside of the brackets. Essentially we just write it in the form (x+a)^2 where a is 1/2 of the constant in front of the x term originally (we found this was 10/14=5/7\r
\n" ); document.write( "\n" ); document.write( "So we have:
\n" ); document.write( "\"7%28x%2B5%2F7%29%5E2%2B2-25%2F7=0\"
\n" ); document.write( "\"7%28x%2B5%2F7%29%5E2%2B14%2F7-25%2F7=0\"
\n" ); document.write( "\"7%28x%2B5%2F7%29%5E2-11%2F7=0\"\r
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\n" ); document.write( "\n" ); document.write( "Now it is just solving for x, so let's isolate x:
\n" ); document.write( "\"7%28x%2B5%2F7%29%5E2-11%2F7=0\"
\n" ); document.write( "\"7%28x%2B5%2F7%29%5E2=11%2F7\"
\n" ); document.write( "\"7%28x%2B5%2F7%29%5E2%2F7=%2811%2F7%29%2F7\"
\n" ); document.write( "\"%28x%2B5%2F7%29%5E2=11%2F49\"
\n" ); document.write( "\"%28x%2B5%2F7%29=%2B-sqrt%2811%2F49%29\"
\n" ); document.write( "\"x=%2B-sqrt%2811%2F49%29-5%2F7\"\r
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\n" ); document.write( "\n" ); document.write( "This can be simplified on your calculator... but I will leave that to you.
\n" ); document.write( "Hopefully this helps... let me know if you are still unsure.
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