Quadratic function (word problem)

Question

henry jumps from a platform 10 meters above the surface of the water. the height of henry's jump can be modeled by the function h(t) = -5.3t^2 + 4.8t +10, where t is time in seconds after the jump. at what time (t) is henry 3 meters above the water?

 

I really need help answering these questions!

Answer 1

Set  h(t)=3.

 

-5.3t² + 4.8t + 10 = 3

 

 

Subtract 3 on both sides of the equation.

 

-5.3t² + 4.8t + 7 = 0

 

 

Use the quadratic formula to solve for the positive value of t.  You can do this last part.