document.write( "Question 147844: Jake Johnson dives off the high dive at a pool. His distance from the surface of the water varies quadratically with the number of seconds that have passed since he left the board. His distances at times of 1, 2, and 3 seconds since he left the board are 24, 18, and 2 meters above the water, respectively.
\n" ); document.write( "How do you write the particular equation expressing distance in terms of time?
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Algebra.Com's Answer #108250 by josmiceli(19441)\"\" \"About 
You can put this solution on YOUR website!
This is distance, \"d\" as a funtion of time
\n" ); document.write( "Here is the most general way to express it as a quadratic:
\n" ); document.write( "\"d%28t%29++=+a%2At%5E2+%2B+b%2At+%2B+c\"
\n" ); document.write( "There are \"3\" different snapshots of the dive, so that
\n" ); document.write( "should give me \"3\" equations, and I should be able to
\n" ); document.write( "find \"a\", \"b\", and \"c\"
\n" ); document.write( "\"24+=+a%2A%281%29%5E2+%2B+b%2A%281%29+%2B+c\"
\n" ); document.write( "\"18+=+a%2A%282%29%5E2+%2B+b%2A%282%29+%2B+c\"
\n" ); document.write( "\"2+=+a%2A%283%29%5E2+%2B+b%2A%283%29+%2B+c\"
\n" ); document.write( "Now figure out the square terms
\n" ); document.write( "\"24+=+a+%2B+b+%2B+c\"
\n" ); document.write( "\"18+=+4a+%2B+2b+%2B+c\"
\n" ); document.write( "\"2+=+9a+%2B+3b+%2B+c\"
\n" ); document.write( "I'll multiply the 2nd equation by \"3\", and the 3rd one by \"2\"
\n" ); document.write( "\"54+=+12a+%2B+6b%2B+3c\"
\n" ); document.write( "\"4+=+18a+%2B+6b+%2B+2c\"
\n" ); document.write( "Now subtract
\n" ); document.write( "\"50+=+-6a+%2B+c\"
\n" ); document.write( "Now subtract the 1st from the 2nd
\n" ); document.write( "\"-6+=+3a+%2B+b+\"
\n" ); document.write( "Multiply by \"2\"
\n" ); document.write( "\"-12+=+6a+%2B+2b\"
\n" ); document.write( "Add
\n" ); document.write( "\"38+=+2b+%2B+c\"
\n" ); document.write( "Subtract thre 3rd one from this
\n" ); document.write( "\"36+=+-9a+-+b\"
\n" ); document.write( "\"b+=+-9a+-+36\"
\n" ); document.write( "\"-6+=+3a+%2B+%28-9a+-+36%29\"
\n" ); document.write( "\"-6+=+3a+-+9a+-+36\"
\n" ); document.write( "\"6a+=+-30\"
\n" ); document.write( "\"a+=+-5\"
\n" ); document.write( "\"50+=+-6%2A%28-5%29+%2B+c\"
\n" ); document.write( "\"50+=+30+%2B+c\"
\n" ); document.write( "\"c+=+20\"
\n" ); document.write( "\"38+=+2b+%2B+20\"
\n" ); document.write( "\"2b+=+18\"
\n" ); document.write( "\"b+=+9\"
\n" ); document.write( "So, the equation I come up with is:
\n" ); document.write( "\"d%28t%29++=+a%2At%5E2+%2B+b%2At+%2B+c\"
\n" ); document.write( "\"d%28t%29+=+-5t%5E2+%2B+9t+%2B+20\" answer
\n" ); document.write( "Let's see if it satisfies the data given
\n" ); document.write( "\"d%281%29+=+-5%2A1%5E2+%2B+9%2A1+%2B+20\"
\n" ); document.write( "\"24+=+-5+%2B+9+%2B+20\"
\n" ); document.write( "\"24+=+24\"
\n" ); document.write( "OK
\n" ); document.write( "\"d%282%29+=+-5%2A2%5E2+%2B+9%2A2+%2B+20\"
\n" ); document.write( "\"18+=+-20+%2B+18+%2B+20\"
\n" ); document.write( "\"18+=+18\"
\n" ); document.write( "OK
\n" ); document.write( "\"d%283%29+=+-5%2A3%5E2+%2B+9%2A3+%2B+20\"
\n" ); document.write( "\"2+=+-45+%2B+27+%2B+20\"
\n" ); document.write( "\"2+=+2\"
\n" ); document.write( "OK
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