Đáp án:
$a,(x-1) ²+(x+3) ²=2(x-2)(x+1)+38$
$=> x²-2x+1+x²+6x+9=(2x-4)(x+1)+38$
$=> x²-2x+1+x²+6x+9=2x²+2x-4x-4+38$
$=> x²+x²-2x²-2x+6x-2x+4x+1+9+4-38=0$
$=> 6x-24=0$
$=> 6x=24$
$=> x=4$
Vậy $S=${$4$}
$b,5(x ²-2x-1)+2(3x-2)=5(x+1) ²$
$=> 5x²-10x-5+6x-4=5(x²+2x+1)$
$=> 5x²-10x-5+6x-4=5x²+10x+5$
$=> 5x²-5x²-10x+6x-10x-5-4-5=0$
$=> -14x - 14 =0$
$=> -14x = 14$
$=> x=-1$
Vậy $S=${$-1$}
BẠN THAM KHẢO NHA!!!