This can be solved in two ways: With heavy tools or with just algebra.
What is your level? Have you studied calculus?

With pure algebra:
We need to find the maximum of the function <span>h = −16t^2 + 36t + 5
Lets take out -1 for simplicity:
</span><span>h = −(16t2 - 36t - 5)
For now lets just work with this: </span>16t^2 - 36t - 5
16t^2=(4t)^2
(4t-x)^2= 16t^2-2*4xt+x^2
we have -36t so x should be 4.5 as 2*4*4.5=36

Lets see what we have now:
16t^2 - 36t - 5= (4t-4.5)^2 is this true? No but close
(4t-4.5)^2= 16t^2- 2*4*4.5t +4.5^2= 16t^2-36t+20.25

16t^2 - 36t - 5 and 16t^2-36t+20.25 nearl the same just take away 25.25 from the right hand side

Getting long, just stay with me:
16t^2 - 36t - 5= (4t-4.5)^2 - 25.25

h= -{(4t-4.5)^2 -25.25}
h=-(4t-4.5)^2 + 25.25

We want to find the maximum of this function. -(4t-4.5)^2 this bit is always negative or 0, so it maximum is when it is 0. Solve: 4t-4.5=0
t=1,125

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3 years ago