<p>Hey guys,</p>
<p>I'd love some help with these math questions:</p>
<h1>18 from page 773</h1>
<p>h(t) = c - (d - 4t)^2 </p>
<p>At time t = 0, a ball was thrown upward from an initial height of 6 feet. Until the ball hit the ground, its height, in feet, after t seconds was given by the function h above, in which c and d are positive constants. If the ball reached its maximum height of 106 feet at the time t = 2.5, what was the height, in feet, of the ball at t = 1?</p>
<h1>19 from page 790</h1>
<p>If k, n, x, and y are positive numbers satisfying x^(-4/3) = k^2 and y^(4/3) = n^2, what is (xy)^(-2/3) in terms of n and k?</p>
<p>106=106-(d-10)^2
d=10
h=106-(10-4)^2
h=70</p>
<p>k=x^(-4/4)
k=1/x
n=y^(4/6)
n=y^(2/3)</p>
<p>(n^(3/2)/k)^(-2/3)=n^(-1)/k^(-2/3)=
(k^(2/3))/n</p>
<p>I think that is correct. It is confusing to do exponents on text :(.</p>
<p>
</p>
<p>Where did you get c = 106 ?</p>
<p><a href=“n%5E(3/2)/k”>quote</a>^(-2/3)=n^(-1)/k^(-2/3)=
(k^(2/3))/n
[/quote]
</p>
<p>The correct answer is 1/nk, not k^(2/3))/n</p>
<p>C=106 because we must include the max. height in the equation. You just wanted to solve for D so you could plug in t=1</p>
<p>Oops My bad @ “k=(-4/4)” it should have been k=(-4/6)</p>
<p>Making (n^(3/2))/(k^(4/6)^(-2/3)= (n^(-1))/k=1/nk</p>
<p>Oh!!! I see now…I wasn’t looking at the equal logically. Thanks!</p>