bài này là quy tắc dấu ngoặc nhưng mik lười đánh à
P=y-[y-(2x-x-y)]=y-[y-x+y]=y-y+ x-y=x-y
Q=y-[y-x+2x-2y]=y-[-y+x]=y+y-x=2y-x
=>P+Q=x-y+2y-x=(x-x)+(2y-y)=y
=>P-Q=(x-y)-(2y-x)=x-y-2y+x=2x-3y
rhreh
gjjjjjjjjjj
ggggggggggggg
ggggggggggggggg
gggggghhhhhhhhh
ffffffff
ayjrte
DANG HOC NGOAI NGU NHU MA CHEN TOAN VO MAY BI DIEN A THANG KIA