Melody

think about the first quadrant of a unit circle..

The unit circle is the circle with a radius of 1 and a centre of (0,0)

The fist quadrant covers angles 0 to pi/2.   

At first only consider proper acute angles. 

You should watch this video - it is very good.   :)

MATHS IS EVERYWHERE!!!

what is the question? 

Start by multiplying both sides by 6*7    (42)   this will get rid of all the fractions.

Remember to put the LHS in brackets first.     :)

I am not sue that I am understanding this properly but

Proposition Y states that the money is behind door A or B

if Y is not tue then the money cannot lie behind A or B which means that proposition X must also be untrue.

                  (it would also mean that there was no money)

BUT

we are told that either X or Y is true so therefore  Y must be true and there must be money behind A or B.

If Y is true then X must be false so the money is not behind door A.

THEREFORE

The money must be behind door B.   Since I want the money I shall open door B

-----------------------------------------------------

I probably did not understand the question properly because I did not even need to make it this complicated.

X : it is behind A

Y:  it is behind A or B

only one is true so it must be behind B

$$\\(2x+1)(4x-3)\\
=2x(4x-3)+1(4x-3)\\
=8x^2-6x+4x-3\\
=8x^2-2x-3$$

That is a shocker of a description.  ;)

@@ End of Day Wrap   Mon 16/3/15     Sydney, Australia Time   10:25 pm     ♪ ♫

Why is RS negative?   Isn't it a length?

Are you sure you have included ALL the information.  It looks like something is missing to me.