The number of books that can be shelved is 45. So then we know that the amount that need to be shelved <em>can</em> be 45, if the bookshelf had 0 books on it. This means that it can have the equal part of the inequality sign.
However, the amount of book that need to be shelved cannot <em>exceed</em> 45, so b must be less than 45.
Therefore, the answer must be D) b ≤ 45.
Answer: see proof below
<u>Step-by-step explanation:</u>
Use the Sum & Difference Identity: cos (A + B) = cos A · cos B - sin A · sin B
Recall the following from Unit Circle: cos (π/2) = 0, sin (π/2) = 1
cos (π) = -1, sin (π) = 0
Use the Quotient Identity: 
<u>Proof LHS → RHS:</u>
Quotient: tan x
LHS = RHS 
6x²+x-12
the first thing we need to do is find 2 numbers that add up to equal the middle term (1) but multiply together to get a product of -72 (-12*6)
two numbers that would fit this is 9 and -8
so now we placed 9x and -8x in place of the middle term
6x²+9x-8x-12
now we look for whats common between the first two numbers and divide them out
6x²+9x = 3x(2x+3)
now we do the same with the last two numbers
-8x-12 = -4(2x+3)
notice how the numbers in brackets are the same (2x+3)
we will keep (2x+3) and then combine the numbers on the outside
once we do that you should get an answer of
(3x-4)(2x+3)
hope this helped!
