SOLUTION: A ball is thrown from an initial height of 3 meters with an upward velocity of 15 m/s. The balls height “h” (in meters) after “t” seconds is given by the following. H=3+15

Algebra ->  Rate-of-work-word-problems -> SOLUTION: A ball is thrown from an initial height of 3 meters with an upward velocity of 15 m/s. The balls height “h” (in meters) after “t” seconds is given by the following. H=3+15      Log On


   



Question 1146642: A ball is thrown from an initial height of 3 meters with an upward velocity of 15 m/s. The balls height “h” (in meters) after “t” seconds is given by the following.
H=3+15t-5t^2
Find all values of “t” for which the bald height is 11 meters.
Round to nearest hundredth

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+h+=+3+%2B+15t+-+5t%5E2+
+11+=+3+%2B+15t+-+5t%5E2+
+-5t%5E2+%2B+15t+-+8+=+0+
----------------------------------
+t+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
+a+=+-5+
+b+=+15+
+c+=+-8+
+t+=+%28-15+%2B-+sqrt%28+15%5E2+-+4%2A%28-5%29%2A%28-8%29+%29%29%2F%282%2A%28-5%29%29+
+t+=+%28-15+%2B-+sqrt%28+225+-+160+%29%29%2F%28+-10+%29+
+t+=+%28+-15+%2B-+sqrt%28+65+%29+%29+%2F+%28-10%29+
+t+=+%28+-15+%2B+8.06226+%29+%2F+%28-10%29+
+t+=+%28+-6.93774+%29+%2F+%28-10+%29+
+t+=+.69377+ sec
and, also:
+t+=+%28+-15+-+8.06226+%29+%2F+%28-10%29+
+t+=+23.06226+%2F+10+
+t+=+2.3062+ sec
----------------------------
+graph%28+400%2C+400%2C+-2%2C+6%2C+-2%2C+15%2C+-5x%5E2+%2B+15x+%2B+3+%29+
The answers look correct -check my math