If 4x² + y² = 40 and xy = 6, then find the value of 2x + y.

if x+y =3 and $${1\over x}+{1\over y}= -{3\over 10}$$ then the value of (x²+y²) is :

Simplify the following expression.

$${\left({375+125} \right)^2-\left({125-375} \right)^2}\over 375×375-125×125$$

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

If α, β are the roots of 6x²+13x+7=0, then the equation whose roots are α², β² is:

 if $$x^4+{16\over x^4}=15617, x>0$$ then find the value of $$x+{2\over x}$$

What is the value of a²+b²+c²-2ab-2bc+2ca?

if $$a+{1\over a}=5$$, then what is the value of $$a^3+{1\over a^3}$$