<p>There is a diagram involved. so you need to have the book to answer it. The answer is D but I would argue that I. is not true. The shaded region only extends to (0,0) so in order for I to be true, it has to say 0</= a </= 4.</p>
<p>Can somebody point out why I am wrong?</p>
<p>0</= a </= 4 is more acurate, but that doesn't make a</= 4 wrong.</p>
<p>it's like, you are between 10 and 20 years old, and it's logic to say you're under 20. get it?</p>
<p>that's what i tried to tell myself but i don't think thats logically sound. your example is a good analogy. yet, if you told me you were between 10 an 20 and the basis is that you are under 20...i might say you are 7. that would definitely satisfy your criteria yet it would not give the correct answer.</p>
<p>If a<=4 then 0<=a<=4 does not have to be true.
If 0<=a<=4 then a<=4 must be true.</p>