Câu 1:
$(P): y=ax^2+bx+c$
$M(4;0)\in (P)\Rightarrow 16a+4b+c=0$ (1)
$S(2;-1)\in (P)\Rightarrow 4a+2b+c=-1$ (2)
Đỉnh S nên $x_S=\dfrac{-b}{2a}=2$
$\Rightarrow 4a+b=0$ (3)
(1)(2)(3)$\to a=\dfrac{1}{4}; b=-1; c=0$
Vậy $(P): y=\dfrac{1}{4}x^2-x$
Câu 2:
$A$ \ $B=[3;5)$
Câu 3:
$A=(A$ \ $B)\cup(A\cap B)=(-3;2)$
$B=(B$ \ $A)\cup(A\cap B)=(1;4)$