document.write( "Question 757031: Choose the real solutions of the system:
\n" ); document.write( "x = (y^2) + -9 and x - 4y - 12 = 0
\n" ); document.write( " I tried using the substitution method but I keep getting stuck! \n" ); document.write( "

Algebra.Com's Answer #460567 by josgarithmetic(39620) $\"\"$ $\"About$

You can put this solution on YOUR website!
x = (y^2) + -9 and x - 4y - 12 = 0 \r
\n" ); document.write( "\n" ); document.write( " $\"x=4y%2B12\"$ from second equation. Substitute into the first equation.\r
\n" ); document.write( "\n" ); document.write( " $\"4y%2B12=y%5E2-9\"$
\n" ); document.write( " $\"y%5E2-4y-9-12=0\"$
\n" ); document.write( " $\"y%5E2-4y-21=0\"$
\n" ); document.write( "You should no longer be stuck. The lefthand side is factorable.\r
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\n" ); document.write( "Just a little bit of review:\r
\n" ); document.write( "\n" ); document.write( " $\"%28x%2Bh%29%28x%2Bk%29=x%5E2%2B%28h%2Bk%29x%2Bhk\"$ \r
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\n" ); document.write( "\n" ); document.write( "If you find some square trinomial as any general $\"x%5E2%2Bax%2Bb\"$ and you want to factor it, try thinking of it as $\"x%5E2%2Bax%2Bb=x%5E2%2B%28h%2Bk%29x%2Bhk\"$
\n" ); document.write( "So you are looking for two numbers, h and k, so that hk=b and h+k=a.
\n" ); document.write( "What you do is look for all the two-number factorizations for b, and find which ones give you a sum of a. We then test each combination until we find something that works. There is a somewhat more analytical way also, but the search and test method is usually enough. \n" ); document.write( "

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