If $$ {x+{1\over x}=7}$$ then $$ {x^{2}+{1\over {x^{2}}}=?}$$

If $$64^{x+1}={64\over 4^x}$$, then the value of x

 If 3x²-5x+1=0, then the value of ( $$x^2+{1\over 9x^2}$$) is 

If a, b are rational number and (a-1)√2+3=b√2+a, the value of (a+b) is : 

If 15x² – 26x + 8 = (Ax + B) (Cx + D), where A and C are positive integers, then what is the value of (2A + B – C – 2D) ?

If $$ {a={1+x\over 2-x}}$$, then find the value $$ {1\over {a+1}}+{2a+1\over{a^{2}-1}}$$ ?

if x⁴+y⁴+x²y²=21 and x²+y²-xy=7, then what is the value of  $${x\over y}+{y\over x}=?$$

If (x + 6y) = 8, and xy = 2, where x > O, what is the value of (x³+216y³)?