Cho a,b,c > 0

CMR \(\frac{a}{b+c}+\frac{b}{c+a}+\frac{c}{a+b}\)≥ \(\frac{3}{2}\)

Nguyên tử R ở chu kì 3 tạo với hợp chất oxi có công thức R203. Trong R số hạt mang điện hơn hạt không mang điện là 11. Khi cho m tdv dd HNO3 dư thu được 20,16 lít NO2(đktc).

Tính m

Tính góc nhập xạ của tp Hồ Chí Minh và Hà Nội vào 2 ngày 25/ 5 và 20/7

Giúp em với em cần gấp lắm ạ

Most people relate stress to physical symptoms like an upset stomach or headaches. Research has suggested that negative emotions and thoughts may also have close links to our brain. Researchers have started finding out why we tend to remember negative things more strongly and in more detail than good ones. "The brain handles positive and negative information in different parts. Negative emotions involve more thinking, and the information is processed more thoroughly. Thus, we tend to ruminate more about unpleasant events and use stronger words to describe them than happy ones," said Clifford Nass, a professor at Stanford University.

Rick Hanson also shares the idea that our minds naturally focus on the bad and discard the good. He stated, "negative stimuli produce more neural activity than do equally intense positive ones. They are also perceived more easily and quickly." This was obtained from his little experiment in which twenty people were asked to look at pictures showing anger or happiness. The participants could identify angry faces faster than happy ones even if it was so quickly.

In a journal article Baumeister co-authored in 2001, "Bad is Stronger Than Good", he concluded, "bad emotions, bad parents and bad feedback have more impact than good ones." This is "a basic and wide-ranging principle of psychology". Thus, Baumeister and his colleagues noted that bad incidents, such as losing your dreamy job and breaking up with your girlfriend or boyfriend, may have a greater impact than landing a job or receiving a marriage proposal.

1People have generally related stress to __________.
A. physical symptoms
B. brain damage
C. ruined relationships with other people
2.Positive events take __________ to perceive than/as negative ones.
A. less time
B. more time
C. the same amount of time
3.Positive things __________.
A. do not produce neural activity
B. produce more neural activity than negative ones
C. produce less neural activity than negative ones
4.The best title for the above text is __________.
A. Stress makes us tired
B. People try to forget bad events.
C. Bad events have stronger impacts than good ones

Hai nguyên tố a, b (Za<Zb) thuộc cùng chu kỳ ở hai nhóm A liên tiếp tổng Z nguyên tử của chũng là 33 . Xác định vị trí của a trong BTH

Nguyên tố R có hai đồng vị, có nguyên tử khối trung bình là 35,5. Hai đồng vị hơn kém nhau 2 nơtron. Tỉ lệ số nguyên tử của hai đồng vị này hơn kém nhau 3 lần. Xác định số khối của hai đồng vị

(1) CaO + H20 -> Ca(OH)2

nCaO = \(\frac{11,2}{56}\) = 0,2 mol

(1) => n Ca(OH)2 = nCaO = 0,2 mol

ta có : n CaCO3 = 2,5 / 100 = 0,025 mol

Xét th 1 : CO2 hết và Ca(OH)2 dư

Ca(OH)2 + CO2 -> CaCO3 + H2O (2)

(2) => nCa(oh)2 = 0,025 mol

=> V co2 = 0,56 lít

Xét th2 : CO2 dư

CO2 + Ca(OH)2 -> CaCO3 + H20 (3)

CO2 + CaCO3 + H2O -> Ca(HCO3)2 (4)

(3), (4) = >n CO2= 0,375 mol

=> Vco2 = 0,375 " 22,4 = 8,4 lít