B= (n+3)²- (n-4)² = (n+3-n+4)(n+3+n-4)= 7(2n-1)
Để B là số nguyên tố <=> 2n-1 =1 <=> n=1
Thử lại n=1 thì B= 7
=> n=1 thì B là số nguyên tố
Đáp án:
Giải thích các bước giải:
Cho tam giác ABC có góc A = 120, AD là đường phân giác . Chứng minh rằng : 1/AD = 1/AB + 1/AC
Mọi người giải giúp mình với nhaaaaa
Vẽ giùm mk nha , iu nhìu ~~ ( ưu tiên app )
Complete the following passage with an appropriate form of the word in BLOCK CAPITAL. Most people seem to think that in order to become healthier, we need to go to the gym every day and eat (0 HARD)______hardly______anything. This is, however, is really not the way to go about changing your (1 HEALTH) ____________ habits. Just a few minutes, basic changes to our daily routine can improve our health (2 DRAMATICAL). If you are the kind of person who keeps trying to exercise regularly but keeps failing, it's time to think again about your attitude. It's important not to focus on your (3 FAIL) ____________, but instead be positive about your (4 SUCCEED) ____________ Instead of being (5.HAPPY) because you didn't go to the gym five times last week, be proud of the fact that at least you went twice. One good reason to eat healthily is that it could improve your mood. A recent survey has found that 80 per cent of people felt (6 GOOD) ____________ when they changed what they ate or drank. A quarter of them said their bad mood and stress (7 APPEAR) ____________ The greatest benefit was after drinking more water, eating more vegetables, (8 REDUCE) ____________ sugar and cutting down on coffee. Another way of improving your mood and lessening stress is to take care when you do things. If you start something, make sure you finish it - even if it is a minor task. Doing so can make you feel happier. When you get close to achieving something, your brain sends out reward signals that make you feel positive. Finally you should make sure that you get plenty of sleep. Don't have too many late nights, although an occasional one won't do you any (9 HARMFUL) ____________Without sleep, the brain can't work properly and you'll get (10 DEPRESS) ____________ So look after your body and your body will look after you.
n=2/3.4+2/4.5+2/5.6+......+2/99.100
tìm hai số biểu số thứ nhất gấp 3 lần số thứ hai và hiệu hai số là 26
Cho tớ hỏi K2ZnO2 có tan trong nước ko?, Nếu có thì ghi pt nhiệt phân K2ZnO2
√2- √8 √2 √8 √2+ √3 · √2- √3
Tính thế điện cực chuẩn Eo của những cặp oxi hóa – khử sau : a) Eo(Cr3+/Cr) b) Eo(Mn2+/Mn)
giải hộ mình theo cách phg pháp đổi biến số với ạ
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