Question 1206027
.
A diver jumps from a springboard. The function h(t) = −5t² + 8t + 4
shows the height of the diver above the water, in meters, t seconds
after the diver leaves the springboard. What time, in seconds, did the
diver start his descent?
Ⓐ 0.4
Ⓑ 0.8
Ⓒ 2
Ⓓ 4
~~~~~~~~~~~~~~~


<pre>
The diver starts his descent at the highest point, so we need find the vertex
of the parabola

    {{{t[max_height]}}} = {{{-b/(2a))}}}, where a= -5 is the coefficient at t^2;

                                   b= 8 is the coefficient at t.

    {{{t[max_height]}}} = {{{(-8)/(2*(-5))}}} = {{{8/10}}} = 0.8 seconds.    <U>ANSWER</U>
</pre>

Solved.


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On finding maximum/minimum of a quadratic function see the lessons

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/quadratic/lessons/HOW-TO-complete-the-square-of-a-quadratic-function-to-find-its-minimum-maximum.lesson>HOW TO complete the square to find the minimum/maximum of a quadratic function</A>

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/quadratic/lessons/Briefly-on-How-to-complete-the-square-of-a-quadratic-function-to-find-its-minimum-maximum.lesson>Briefly on finding the minimum/maximum of a quadratic function</A>

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/quadratic/lessons/HOW-TO-complete-the-square-to-find-the-vertex-of-a-quadratic-function.lesson>HOW TO complete the square to find the vertex of a parabola</A>

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/quadratic/lessons/Briefly-on-finding-the-vertex-of-a-parabola.lesson>Briefly on finding the vertex of a parabola</A>

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