document.write( "Question 582171: The number of horsepower, H, needed to overcome a wind drag on an automobile is given by H=0.005s^2 + 0.007s - 0.031, where s is the speed of the car in miles per hour. At what speed will the car need to travel to use 200 horsepower to overcome the wind drag?
\n" ); document.write( "I tried this several ways and still came up with 199.32 miles per hour which my teacher says is wrong.
\n" ); document.write( "Please help. \n" ); document.write( "

Algebra.Com's Answer #371980 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
$\"+H+=+.005s%5E2+%2B+.007s+-+.031+\"$
\n" ); document.write( "given:
\n" ); document.write( " $\"+200+=+.005s%5E2+%2B+.007s+-+.031+\"$
\n" ); document.write( "-----------------------------
\n" ); document.write( "Multiply both sides by $\"+1000+\"$
\n" ); document.write( " $\"+200000+=+5s%5E2+%2B+7s+-+31+\"$
\n" ); document.write( " $\"+5s%5E2+%2B+7s+-+200031+=+0+\"$
\n" ); document.write( " $\"+5s%5E2+%2B+7s+=+200031+\"$
\n" ); document.write( "Divide both sides by $\"5\"$
\n" ); document.write( " $\"+s%5E2+%2B+%287%2F5%29%2As+=+200031%2F5+\"$
\n" ); document.write( "I'll try completing the square
\n" ); document.write( " $\"+s%5E2+%2B+%287%2F5%29%2As+%2B+%287%2F10%29%5E2+=+200031%2F5+%2B+%287%2F10%29%5E2+\"$
\n" ); document.write( " $\"+s%5E2+%2B+%287%2F5%29%2As+%2B+49%2F100+=+200031%2F5+%2B+49%2F100+\"$
\n" ); document.write( " $\"+s%5E2+%2B+%287%2F5%29%2As+%2B+49%2F100+=+4000620%2F100+%2B+49%2F100+\"$
\n" ); document.write( " $\"+s%5E2+%2B+%287%2F5%29%2As+%2B+49%2F100+=+4000669%2F100+\"$
\n" ); document.write( " $\"+%28+s+%2B+.7+%29%5E2+=+%28+2000.1672%2F10+%29%5E2+\"$
\n" ); document.write( "Take the square root of both sides
\n" ); document.write( " $\"+s+%2B+.7+=+200.01672+\"$
\n" ); document.write( " $\"+s+=+200.01672+-+.7+\"$
\n" ); document.write( " $\"+s+=+199.31672+\"$
\n" ); document.write( "-----------------
\n" ); document.write( "I'll check this
\n" ); document.write( " $\"+H+=+.005%2A199.32%5E2+%2B+.007%2A199.32+-+.031+\"$
\n" ); document.write( " $\"+H+=+.005%2A39728.462+%2B+1.395+-+.031+\"$
\n" ); document.write( " $\"+H+=+198.642+%2B+1.395+-+.031+\"$
\n" ); document.write( " $\"+H+=+200.0063+\"$
\n" ); document.write( "This seems very close to the right answer.
\n" ); document.write( "Are we both making the same mistake?
\n" ); document.write( "The other possibility is you copied the
\n" ); document.write( "problem wrong ( or your teacher did ).
\n" ); document.write( "Did anyone get the right answer? \n" ); document.write( "

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