Completing The Square Generalized

If the function $y=(x^2-2x)^2+16x^2-32x$ has the minimum value $b$ at $x=a$ , what is $a-b$ ?

For $x>0$ , the function $y=-x^4+18x^2-74$ has a maximum value $y=b$ at $x=a$ . What is $a+b$ ?

What is the sum of the maximum and minimum values of $y=(x^2-2x+8)^2-16(x^2-2x+8)+84$ in the domain $0 \leq x \leq 3$ ?

For $x>0$ , the function $y=x^4-10x^2+31$ has a minimum value $y=b$ at $x=\sqrt{a}$ . What is $a+b$ ?

For $x>0$ , the function $y=-x^4+8x^2-4$ has a maximum value $y=b$ at $x=a$ . What is $a+b$ ?