document.write( "Question 200633: If an object is projected upward with an initial velocity of 48 ft pe second from a height h of 160 ft, then its height t second after it is projected is defined by the equation h= -16t 2 + 48t + 160. How many seconds after it is projected will it hit the ground? \n" ); document.write( "

Algebra.Com's Answer #150888 by Earlsdon(6294) $\"\"$ $\"About$

You can put this solution on YOUR website!
You are looking for the time, t, when h(t) = 0, so...
\n" ); document.write( " $\"h%28t%29+=+-16t%5E2%2B48t%2B160\"$ Substitute h(t) = 0.
\n" ); document.write( " $\"0+=+-16t%5E2%2B48t%2B160\"$ Rewrite in standard form:
\n" ); document.write( " $\"-16t%5E2%2B48t%2B160+=+0\"$ First factor -16.
\n" ); document.write( " $\"-16%28t%5E2-3t-10%29+=+0\"$ Notice the change of sign in each term in the parentheses as a result of factoring the -16. Now apply the zero product rule.
\n" ); document.write( " $\"t%5E2-3t-10+=+0\"$ Solve by factoring.
\n" ); document.write( " $\"%28t%2B2%29%28t-5%29+=+0\"$ Apply the zero product rule.
\n" ); document.write( " $\"%28t%2B2%29+=+0\"$ or $\"%28t-5%29+=+0\"$ so then...
\n" ); document.write( " $\"t+=+-2\"$ or $\"t+=+5\"$ Discard the negative solution as the time, t, should be a positive value.
\n" ); document.write( " $\"highlight%28t+=+5%29\"$ seconds. \n" ); document.write( "

\n" );