<p>number 20, pg 401
number 18, pg 418</p>
<p>Thanks!!!</p>
<p>I feel like a math tutor here…</p>
<p>P401, prob.20: 2<em>14000</em>k/100 (notice it’s k percent times price for commision, not k times price.)</p>
<p>P418, prob.18, for g (x) = 0, x = -3, or x = +3. </p>
<p>Now x = a-1.2, if x = -3, a = -3+1.2 = -1.8
if x = +3, the a = +3 + 1.2 = 4.2.
Since the problem says a >0, so a = 4.2</p>
<p>oops!! I meant p401 #19, sorry!!
and yes, I understand #18! thanks so much=)</p>
<p>P401, #9,</p>
<p>let x be the line connecting the top (point V) to the middle of one base (NOT the middle of the pyramid. - I wish I could draw a pic. here but I hope you know what I mean. draw it on the picture you should see well.)
Then you have a right triangle, the hypotenuse is l, long side is x, short side is m/2. </p>
<p>then you have: x^2 + (m/2)^2 = l^2 according to pythagorean theorem.
from this you get x^2 = 3m^2/4.</p>
<p>then you need another right triangle, where the hypotenuse is x, (what you got from the previous step), long side is h, short side is m/2. </p>
<p>Use P-theorem again, you have:
h^2+ (m/2)^2 = x^2 = 3m^2/4 (The last step here is from the result of the previous result for x),
that gives h^2 = (3/4 - 1/2) m^2 which is m^2/2, so h = m/sqrt(2)</p>
<p>Hope it helps.</p>