The height, in feet, of a javelin t seconds after it is thrown is modeled by the function h(t) =-4t^2+24t+6. After how many seconds does the javelin reach its maximum height of 42 feet?

δabc ≅ δdcb by sas because

db ≅ ac . . given (side)

bc ≅ bc . . reflexive property (side)

∠dbc ≅ ∠ acb . . alternate interior angles where transversal bc crosses parallel lines bd and ac (included angle)