Value of $$ \sqrt{6+\sqrt {6+\sqrt {6+....}}}$$

If x + y + z=1, xy+yz+zx=-26 and x³ + y³+z³=151, then what will be the value of xyz?

If (a-b)=-3 , (b-c)=5 and (c-a)=-2, then the value of $$ {a^{3}+b^{3}+c^{3}-3abc\over a+b+c}$$.

If x²+y²-4x-4y+8=0, then the value of x-y is: 

If (a+b)=16 and a³+b³=1456, then what is the value of ab?

If $$ {a^4+1}={{a^2}\over{b^2}}{(4b^2-b^4-1)}$$,then what is the value of $${a^4+b^4}$$?

If a+b=2c, find $${a\over a-c}+{c\over b-c}?$$

If $$ P={{x^2-36}\over{x^2-49}}$$ and $$ Q={{x+6}\over{x+7}}$$ then the value of $$ {P\over{Q}}$$ is.