document.write( "Question 211578This question is from textbook
\n" ); document.write( ": Can someone please help me with this \"ballistics word problem?
\n" ); document.write( "The height of a projectile fired upward with an initial velocity of 400 ft per sec is given by the formula h=-16t^2+400t, where h is the height in ft and t is the time in sec. Find the time required for the projectile to return to earth.
\n" ); document.write( "Please show me the steps and please get back before Tues 10am
\n" ); document.write( "Thank you so much \n" ); document.write( "
Algebra.Com's Answer #159869 by ankor@dixie-net.com(22740)\"\" \"About 
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The height of a projectile fired upward with an initial velocity of 400 ft per sec is given by the formula h=-16t^2+400t, where h is the height in ft and t is the time in sec. Find the time required for the projectile to return to earth.
\n" ); document.write( ":
\n" ); document.write( " h = -16t^2 + 400t
\n" ); document.write( "When the projectile returns to earth, h = 0, therefore:
\n" ); document.write( " -16t^2 + 400t = 0
\n" ); document.write( "factor out -16x
\n" ); document.write( "-16t(t - 25) = 0
\n" ); document.write( "our solution
\n" ); document.write( "t = 25 sec to return to earth
\n" ); document.write( ":
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\n" ); document.write( "Check solution in original equation
\n" ); document.write( " -16(25^2) + 400(25) =
\n" ); document.write( "-16(625) + 10000 =
\n" ); document.write( "-10000 + 10000 = 0 \n" ); document.write( "
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