document.write( "Question 907730: An object projected from height of 48 ft. with an initial velocity of 32 ft./sec after t seconds has a height = -16t^2 + 32t +48.
\n" ); document.write( "A) After how many seconds is the height 64 ft?
\n" ); document.write( "B) After how many seconds does the object hit the ground?
\n" ); document.write( "C) How high is the object after 1/2 second?\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "I'm not entirely confident with my answers but here is what I got:
\n" ); document.write( "A) 1 second
\n" ); document.write( "B) 3 seconds
\n" ); document.write( "C) 60 feet
\n" ); document.write( "I just need help to see if I understood this correctly. I was having a very difficult time with this problem.
\n" ); document.write( "

Algebra.Com's Answer #550531 by KMST(5328)\"\" \"About 
You can put this solution on YOUR website!
THE REASONING:
\n" ); document.write( "A) \"system%28height+=+-16t%5E2+%2B+32t+%2B48%2C+height=64%29\"--->\"64=+-16t%5E2+%2B+32t+%2B48\"
\n" ); document.write( "You solved that equation correctly and found \"t=1\" .
\n" ); document.write( "B) \"system%28height+=+-16t%5E2+%2B+32t+%2B48%2C+height=0%29\"--->\"0=+-16t%5E2+%2B+32t+%2B48\"
\n" ); document.write( "You solved that equation correctly and found \"t=3\" .
\n" ); document.write( "C) \"system%28height+=+-16t%5E2+%2B+32t+%2B48%2C+t=1%2F2%29\"--->\"height+=+-16%281%2F2%29%5E2+%2B+32%281%2F2%29+%2B48=-16%281%2F4%29%2B16%2B48=-4%2B16-48=60\" ,
\n" ); document.write( "and you did the calculation correctly.
\n" ); document.write( "
\n" ); document.write( "THE QUADRATIC EQUATIONS:
\n" ); document.write( "There are many ways to solve. This is my way.
\n" ); document.write( "\"64=+-16t%5E2+%2B+32t+%2B48\"
\n" ); document.write( "\"64-48=+-16t%5E2+%2B+32t\"
\n" ); document.write( "\"16=+-16t%5E2+%2B+32t\"
\n" ); document.write( "(Here I would say that I am dividing both sides of the equal sign by -16,
\n" ); document.write( "but I think of it as two steps)
\n" ); document.write( "Dividing both sides of the equation by 16, we get
\n" ); document.write( "\"1=-t%5E2%2B2\" , and changing the signs (multiplying both sides times -1), we get
\n" ); document.write( "\"t%5E2-2t=-1\"
\n" ); document.write( "Adding 1 to both sides, I complete the square:
\n" ); document.write( "\"t%5E2-2t%2B1=-1%2B1\"
\n" ); document.write( "\"%28t-1%29%5E2=0\"--->\"t-1=0\"--->\"t=1\"
\n" ); document.write( "
\n" ); document.write( "\"0=+-16t%5E2+%2B+32t+%2B48\"
\n" ); document.write( "Dividing both sides by -16, I would get
\n" ); document.write( "\"t%5E2-2t-3=0\"
\n" ); document.write( "\"t%5E2-2t=3\"
\n" ); document.write( "\"t%5E2-2t%2B1=3%2B1\"
\n" ); document.write( "\"%28t-1%29%5E2=4\"--->\"t-1=2\"--->\"t=3\"
\n" ); document.write( "
\n" );