<p>These are just some questions I found from Meylani’s practice test (old edition) that I thought might either have errors in them, or that I just don’t get it. Somebody explain it to me. </p>
<li><p>the relation x^2/25 - y^2/144=1 has how many of the following type of sym?
-sym about origin, x-axis,y-axis,y=x,y=-x
Answer is 3. X-axis, y-axis, and origin. But the test for odd function fails and it doesnt look like it has sym about the origin. Error?</p></li>
<li><p>if a and b are positive integers such that 6/7<a/b<7/8 then whta is the smallest b?
a. 13
b. 15
c 43
d. 56
e. 112</p></li>
</ol>
<p>Answer is E, 112. I thought it was 15, because if b is 15, a could be 13, which satisfies the equation. </p>
<li>Given that z= t^3-1 and y=3t^2+4. If y-z= 9, t equals?
a. -1
b. 0
c. 1
d. 2
e. 3</li>
</ol>
<p>simple enough, I solved for t. I got t= -1 and 2, which are both choices! Answer is -1, I don’t know why. The solution online did not even mention 2 as a solution. Explain??</p>
<p>Please Explain!! Meylani, if you see this, please explain! These were not part of the Corrections on your website!!!</p>
<ol>
<li><p>You're right, 13/15 satisfies all conditions.</p></li>
<li><p>Plug in each value of t, see if it yields satisfactory values for y-z.
If t=-1, z=(-1)^3-1 = -2 and y=3(-1)^2 + 4= 7; y-z = 9
t=0, z=-1 and y=4
t=1, z=0 and y=7
t=2, z=7 and y=16 y-z = 9
t=3, z=26 and y=31
So I'd say you're right again.</p></li>
<li><p>Since the function uses only x^2, you'll solve for the same value of y when x=a and when x=-a; doesn't that imply symmetry about the origin?</p></li>
</ol>
<p>i get t=radical(2)
sub in y and z, 3t^2+4-t^3+1=p-->2t^2+5=9-->2t^2=4 etc.</p>
<p>Islanders:</p>
<p>I think that's a mix of 3t^2 - t^3 above, not 3t^2 - t^2. You should have a cubic equation in t, not a quadratic.</p>
<p>I guess they are just errors then in the tests</p>
<p>But for #1, I tried the test for odd functions, which imply symmetry about the origin, but the test failed. The test for odd is f(x)=-f(-x)</p>
<p>Agrophobic:
For #1, I'm not sure this qualifies as a function y = f(x), since you don't get a unique value of y for each x. (But it's a long time since I looked up the exact definition of a function :) ).</p>
<p>The test for odd is for any pair (x,y) that is on the graph (-x,-y) is on it. In this case, since x and y are both being squared (and the result is always positive), it does have symettry about the orgin. The other two are errors. In the new version, your second question is included and the answer is 15. And number one is not a function, but the question clearly states it is a relation.</p>