If the equation $${x^2} - cx + d = 0$$ has roots equal to the fourth powers of the roots of $${x^2} + ax + b = 0$$, where $${a^2} > 4b$$, then the roots of $${x^2} - 4bx + 2{b^2} - c = 0$$ will be

If a, b$$ \in $$ {1, 2, 3} and the equation ax² + bx + 1 = 0 has real roots, then

If the equation x² + y² $$-$$ 10x + 21 = 0 has real roots x = $$\alpha$$ and y = $$\beta$$, then