bác An đem trứng ra chợ,sau khi bán đc 2/5 số trứng và 1 quả thì con lại 50 quả trứng. Hỏi lúc đầu bác An bán đc bao nhiêu quả trứng
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de co sai khong ban? Mk nghi phai la 1/2+1/3+1/4+...+1/63 > 2 chu?
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1. Why do people attend the festival?
2. Why do a lot of people go to Da Lat city?
3. How did they celebrate it?
1. People attend the festival for fun.
(?) Why do people attend the festival?
2. A lot of people go to Da Lat city to attend the flower festival.
(?) Why do people go to Da Lat city?
3. People celebrate it with street fairs and live music.
(?) How do people celebrate it?
___Học_tốt___
#lyt
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Ta có:
\(f\left(5\right)=125a+25b+5c+d\)
\(f\left(4\right)=64a+16b+4c+d\)
\(f\left(7\right)=343a+49b+7c+d\)
\(f\left(2\right)=8a+4b+2c+d\)
Xét:
\(f\left(5\right)-f\left(4\right)=125a+25b+5c+d-64a-16b-4c-d\)
\(=61a+9b+c=2019\)
Khi đó:
\(f\left(7\right)-f\left(2\right)=343a+49b+7c+d-8a-4b-2c-d\)
\(=335a+45b+5c=5\left(61a+9b+c\right)+30=5\cdot2019+30⋮5\)
Vậy ta có đpcm
![](https://rs.olm.vn/images/avt/0.png?1311)
AN = 3/4. AC → NC = 1/4.AC. Từ B hạ BH vuông góc AC
Nối BN ta có S∆BNC = 1/2 .NC.BH = 1/2. 1/4.AC.BH
1/4. 1/2 .AC.BH = 1/4.S∆ABC → S∆BNA = 3/4.S∆ABC
từ N hạ NK vuông góc AB ta có AM = 2/3 AB→ MB = 1/3.AB
S∆BNM = 1/2 .NK.BM= 1/2 .NK.1/3AB = 1/3. S∆BNA
→ S∆BNM = 1/3 . 3/4.S∆ABC = 1/4 S∆ABC
Diện tích tứ giác BMNC = S → S = S∆BNC+S∆BNM =120 cm²
→1/4.S∆ABC + 1/4.S∆ABC = 1/2.S∆ABC = 120 cm²
→ S∆ABC = 240 cm²
![](https://rs.olm.vn/images/avt/0.png?1311)
COMPLETE THE DIALOGUE WITH THE WORDS / PHRASES IN THE BOX .
A. Why B.What would you to do C. What would you
D. Who would you E . Where would you
A: ( 1 ) C. What would you to be in the future ?
B: I'd to be a teacher or English .
A:( 2 ) D. Who would you to teach ?
B: Young children .
A: ( 3 ) A. Why ?
B: because I'd to teach them how to speak English .
A: ( 4 ) E.Where would you to work ?
B: In a primary school in the mountainns .
A: ( 5 ) B. What would you to do in your free time ?
B : I'd to care for poor children .
Nếu Bác An chỉ bán 2/5 số trứng thì số trứng còn lại là
50+1=51 quả
Phân số chỉ số trứng còn lại là
1-2/5=3/5 số trứng
Số trứng ban đầu là
51:3/5=85 quả
Só trứng Bác An bán lúc đầu là
85-50=35 quả