document.write( "Question 1079108: Eleven years from now, Peter's age will be half the square of the age he was 13 years ago. Calculate the current age of Peter.
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Algebra.Com's Answer #693483 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
Let $\"+x+\"$ = Peter's current age
\n" ); document.write( "given:
\n" ); document.write( " $\"+x+%2B+11+=+%281%2F2%29%2A%28+x+-+13+%29%5E2+\"$
\n" ); document.write( " $\"+2%2A%28+x+%2B+11+%29+=+x%5E2+-+26x+%2B+169+\"$
\n" ); document.write( " $\"+2x+%2B+22+=+x%5E2+-+26x+%2B+169+\"$
\n" ); document.write( " $\"+x%5E2+-28x+%2B+147+=+0+\"$
\n" ); document.write( "Use quadratic equation
\n" ); document.write( " $\"+x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+\"$
\n" ); document.write( " $\"+a+=+1+\"$
\n" ); document.write( " $\"+b+=+-28+\"$
\n" ); document.write( " $\"+c+=+147+\"$
\n" ); document.write( "----------------
\n" ); document.write( " $\"+x+=+%28+-%28-28%29+%2B-+sqrt%28+%28-28%29%5E2-4%2A1%2A147+%29%29%2F%282%2A1%29+\"$
\n" ); document.write( " $\"+x+=+%28+28+%2B-+sqrt%28+784+-+588+%29%29%2F2+\"$
\n" ); document.write( " $\"+x+=+%28+28+%2B-+sqrt%28+196+%29%29%2F2+\"$
\n" ); document.write( " $\"+x+=+%28+28+%2B+14+%29+%2F+2+\"$
\n" ); document.write( " $\"+x+=+42%2F2+\"$
\n" ); document.write( " $\"+x+=+21+\"$
\n" ); document.write( "Peter is 21 now
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\n" ); document.write( "check:
\n" ); document.write( " $\"+x+%2B+11+=+%281%2F2%29%2A%28+x+-+13+%29%5E2+\"$
\n" ); document.write( " $\"+21+%2B+11+=+%281%2F2%29%2A%28+21+-+13+%29%5E2+\"$
\n" ); document.write( " $\"+32+=+%281%2F2%29%2A8%5E2+\"$
\n" ); document.write( " $\"+32+=+%281%2F2%29%2A64+\"$
\n" ); document.write( " $\"+32+=+32+\"$
\n" ); document.write( "OK
\n" ); document.write( "I'll try the negative root of $\"+196+\"$ also
\n" ); document.write( " $\"+x+=+%28+28+-+14+%29+%2F+2+\"$
\n" ); document.write( " $\"+x+=+14%2F2+\"$
\n" ); document.write( " $\"+x+=+7+\"$
\n" ); document.write( "-----------------
\n" ); document.write( " $\"+x+%2B+11+=+%281%2F2%29%2A%28+x+-+13+%29%5E2+\"$
\n" ); document.write( " $\"+7+%2B+11+=+%281%2F2%29%2A%28+7+-+13+%29%5E2+\"$
\n" ); document.write( " $\"+18+=+%281%2F2%29%2A%28+-6+%29%5E2+\"$
\n" ); document.write( " $\"+18+=+%281%2F2%29%2A36+\"$
\n" ); document.write( " $\"+18+=+18+\"$
\n" ); document.write( "I don't think this is a valid solution since his
\n" ); document.write( "age 13 years ago ends up being 6 years
\n" ); document.write( "before he was born. I'll stick with
\n" ); document.write( "the 1st answer.
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