document.write( "Question 900370: Three parts and uses the quadratic equation: x^2 - 18x + 72 = 0\r
\n" ); document.write( "\n" ); document.write( "Part a.
\n" ); document.write( "1. Graph the quadratic equation and:
\n" ); document.write( "a. Label and include the ordered pair for the vertex on the graph.
\n" ); document.write( "b. Label and include the ordered pair(s) for the x--intercepts on the graph.
\n" ); document.write( "c. How are the solutions identified from the graph?\r
\n" ); document.write( "\n" ); document.write( "Part b.
\n" ); document.write( "1. Solve the quadratic equation by using the \"completing the square\" method.
\n" ); document.write( "2. What do you notice about the answer you found here and where the x-intercepts of the graph are in part a?\r
\n" ); document.write( "\n" ); document.write( "Part c.
\n" ); document.write( "1. Solve the quadratic equation by using the quadratic formula. Show all your work.
\n" ); document.write( "2. Compare your answer to what you found in part a and b. What do you notice about the answers?\r
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Algebra.Com's Answer #548719 by richwmiller(17219)\"\" \"About 
You can put this solution on YOUR website!
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Solved by pluggable solver: COMPLETING THE SQUARE solver for quadratics
Read this lesson on completing the square by prince_abubu, if you do not know how to complete the square.
Let's convert \"1x%5E2%2B-18x%2B72=0\" to standard form by dividing both sides by 1:
\n" ); document.write( "We have: \"1x%5E2%2B-18x%2B72=0\". \n" ); document.write( "What we want to do now is to change this equation to a complete square \"%28x%2Bsomenumber%29%5E2+%2B+othernumber\". How can we find out values of somenumber and othernumber that would make it work?
\n" ); document.write( "Look at \"%28x%2Bsomenumber%29%5E2\": \"%28x%2Bsomenumber%29%5E2+=+x%5E2%2B2%2Asomenumber%2Ax+%2B+somenumber%5E2\". Since the coefficient in our equation \"1x%5E2%2Bhighlight_red%28+-18%29+%2A+x%2B72=0\" that goes in front of x is -18, we know that -18=2*somenumber, or \"somenumber+=+-18%2F2\". So, we know that our equation can be rewritten as \"%28x%2B-18%2F2%29%5E2+%2B+othernumber\", and we do not yet know the other number.
\n" ); document.write( "We are almost there. Finding the other number is simply a matter of not making too many mistakes. We need to find 'other number' such that \"%28x%2B-18%2F2%29%5E2+%2B+othernumber\" is equivalent to our original equation \"1x%5E2%2B-18x%2Bhighlight_green%28+72+%29=0\".
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\n" ); document.write( " The highlighted red part must be equal to 72 (highlighted green part).
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\n" ); document.write( " \"-18%5E2%2F4+%2B+othernumber+=+72\", or \"othernumber+=+72--18%5E2%2F4+=+-9\".
\n" ); document.write( "So, the equation converts to \"%28x%2B-18%2F2%29%5E2+%2B+-9+=+0\", or \"%28x%2B-18%2F2%29%5E2+=+9\".
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\n" ); document.write( " Our equation converted to a square \"%28x%2B-18%2F2%29%5E2\", equated to a number (9).
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\n" ); document.write( " Since the right part 9 is greater than zero, there are two solutions:
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\n" ); document.write( " \"system%28+%28x%2B-18%2F2%29+=+%2Bsqrt%28+9+%29%2C+%28x%2B-18%2F2%29+=+-sqrt%28+9+%29+%29\"
\n" ); document.write( " , or
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\n" ); document.write( " \"system%28+%28x%2B-18%2F2%29+=+3%2C+%28x%2B-18%2F2%29+=+-3+%29\"
\n" ); document.write( " \"system%28+x%2B-18%2F2+=+3%2C+x%2B-18%2F2+=+-3+%29\"
\n" ); document.write( " \"system%28+x+=+3--18%2F2%2C+x+=+-3--18%2F2+%29\"
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\n" ); document.write( " \"system%28+x+=+12%2C+x+=+6+%29\"
\n" ); document.write( "Answer: x=12, 6.\n" ); document.write( "
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Solved by pluggable solver: Quadratic Formula
Let's use the quadratic formula to solve for x:

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\n" ); document.write( " Starting with the general quadratic
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\n" ); document.write( " \"ax%5E2%2Bbx%2Bc=0\"
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\n" ); document.write( " the general solution using the quadratic equation is:
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\n" ); document.write( " \"x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29\"
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\n" ); document.write( " So lets solve \"x%5E2-18%2Ax%2B72=0\" ( notice \"a=1\", \"b=-18\", and \"c=72\")
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\n" ); document.write( " \"x+=+%28--18+%2B-+sqrt%28+%28-18%29%5E2-4%2A1%2A72+%29%29%2F%282%2A1%29\" Plug in a=1, b=-18, and c=72
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\n" ); document.write( " \"x+=+%2818+%2B-+sqrt%28+%28-18%29%5E2-4%2A1%2A72+%29%29%2F%282%2A1%29\" Negate -18 to get 18
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\n" ); document.write( " \"x+=+%2818+%2B-+sqrt%28+324-4%2A1%2A72+%29%29%2F%282%2A1%29\" Square -18 to get 324 (note: remember when you square -18, you must square the negative as well. This is because \"%28-18%29%5E2=-18%2A-18=324\".)
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\n" ); document.write( " \"x+=+%2818+%2B-+sqrt%28+324%2B-288+%29%29%2F%282%2A1%29\" Multiply \"-4%2A72%2A1\" to get \"-288\"
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\n" ); document.write( " \"x+=+%2818+%2B-+sqrt%28+36+%29%29%2F%282%2A1%29\" Combine like terms in the radicand (everything under the square root)
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\n" ); document.write( " \"x+=+%2818+%2B-+6%29%2F%282%2A1%29\" Simplify the square root (note: If you need help with simplifying the square root, check out this solver)
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\n" ); document.write( " \"x+=+%2818+%2B-+6%29%2F2\" Multiply 2 and 1 to get 2
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\n" ); document.write( " So now the expression breaks down into two parts
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\n" ); document.write( " \"x+=+%2818+%2B+6%29%2F2\" or \"x+=+%2818+-+6%29%2F2\"
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\n" ); document.write( " Lets look at the first part:
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\n" ); document.write( " \"x=%2818+%2B+6%29%2F2\"
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\n" ); document.write( " \"x=24%2F2\" Add the terms in the numerator
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\n" ); document.write( " \"x=12\" Divide
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\n" ); document.write( " So one answer is
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\n" ); document.write( " \"x=12\"
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\n" ); document.write( " Now lets look at the second part:
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\n" ); document.write( " \"x=%2818+-+6%29%2F2\"
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\n" ); document.write( " \"x=12%2F2\" Subtract the terms in the numerator
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\n" ); document.write( " \"x=6\" Divide
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\n" ); document.write( " So another answer is
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\n" ); document.write( " \"x=6\"
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\n" ); document.write( " So our solutions are:
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\n" ); document.write( " \"x=12\" or \"x=6\"
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