Hai nhà có số cây là:

​2 + 3 = 5 ( cây)

​Đáp số: 5 cây

Ai k mk thì mk k lại 3 k

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\(y=\frac{1+5+11+19+29+41+55+71+89}{2+6+12+20+30+42+56+72+90}\)

\(y=\frac{1x2-1+2x3-1+3x4-1+4x5-1+5x6-1+6x7-1+7x8-1+8x9-1+9x10-1}{1x2+2x3+3x4+4x5+5x6+6x7+7x8+8x9+9x10}\)

\(y=\frac{\left(1x2+2x3+...+9x10\right)-\left(1+1+1+1+1+1+1+1+1\right)}{1x2+2x3+...+9x10}\)

\(y=\frac{1x2+2x3+...+9x10}{1x2+2x3+...+9x10}-\frac{9}{1x2+2x3+...+9x10}\)

\(y=1-\frac{9}{1x2+2x3+...+9x10}\)

1.We had a river in which we could swim.

-> We had a river to swim in.

2.The child would be happier if he had someone that he could play with.

-> The child would be happier if he had someone to play with.

3.I have some letter that I must write.

-> I have some letter to write.

4.If she had a family that she had to cook for, she would be more interested.

-> If she had a family to cook for she would be more interested.

5.I haven't got anyone that I can go with.

-> I haven't got anyone to go with.

6.There are six letters which have to be written today.

-> There are six letters to be written today.

7.He was the second man who was killed in this way.

-> He was the second man to be killed in this way.

8.Here is the novel that she should read.

-> Here is the novel for she to read.

9.The last man who was interviewed was entirely unsuitable.

-> The last man to be interviewed was entirely unsuitable.

10.I wish i had a box that I could keep my letter in.

-> I wish i had a box to keep my letter in.

hai nhà có số cây xoài là

10+12=22[cây]

đ/s:22 cây xoài

\(\text{Ta có: }\)\(\left(1-\frac{1}{2}\right)\times\left(1-\frac{1}{3}\right)\times\left(1-\frac{1}{4}\right)\times\left(1-\frac{1}{4}\right)\times\left(1-\frac{1}{5}\right)\)

              \(=\frac{1}{2}\times\frac{2}{3}\times\frac{3}{4}\times\frac{3}{4}\times\frac{4}{5}\)

                 \(=\frac{1\times2\times3\times3\times4}{2\times3\times4\times4\times5}\)

                     \(=\frac{1\times3}{4\times5}\)

                      \(=\frac{3}{20}\)

Anh ơi, vòng 1 lần trước em không biết hạn chót là ngày 23 nên tối ngày 24 em mới làm và nộp :((. Hôm sau chị Vy có ib với e là bài em cũng đủ điểm để vào vòng 2 nên xin anh cho em được thi vòng 2 với ạ :((.

16-2=14(viên)