Tổng tổi của 2 bố con là :

25 * 2 = 50 ( tuổi )

Tuổi bố là :

( 50 + 28 ) : 2 = 39 ( tuổi )

Đ/S: 39 tuổi 

giúp mik gấp nhé(thanks)
exercise 4: give the correct word form
1.Today Lien is unhappy (happy)because she misses her parents
2.Nam's new house is bigger (big) than his old house
3. There are 32 classes ( class) in our school
4. He doesn't have many relatives ( relate) in Ha Noi
5.They are talking (talk) to their teacher

exercise 5:rewrite the sintences.
1. It is a good idea to eat a lot of fruit and vegetable everyday
We should eat a lot of fruit and vegetable everyday.
2. we couldn't keep on cleaning the streets because of the heavy rain
Because of the heavy rain, we couldn't keep on cleaning the streets
3.The garden party won't take place if the weather doesn't improve
Unless the weather improves, the garden party won't take place.
4.both students and teachers can borrow books from the libraly
The library lend both students and teachers the books
5.nobody plays this piece of music as beautifully as he does
He plays this piece of music the most beautifully.
6.there is a sink, a tub, and a shower in the bathroom
The bathroom has sink, a tub, and a shower.
7.no one in the group is taller than Trung
Trung is the tallest one in the group.
8.Do you have a better refrigerator than this
Is this the best refrigerator you have?

\(E=\frac{n^2+n+1}{n+1}=\frac{n^2}{n+1}+\frac{n+1}{n+1}=\frac{n^2}{n+1}+1\)

=> \(\frac{n^2}{2+1}\in Z\)

Có: \(n^2\) chia hết cho \(n\) suy ra \(n^2\) không chia hết cho \(n+1\)

Do đó: \(n=0\)

Mặt khác: Để E thuộc Z

=> n+1 = -1 => n = -2

a) \(x^3-x^2-5x+125\)

\(=\left(x+5\right)\left(x^3-5x+25\right)-x\left(x+5\right)\)

\(=\left(x+5\right)\left(x^3-5x+25-x\right)\)

\(=\left(x+5\right)\left(x^3-6x+25\right)\)

CHÂU ÂU NẰM Ở ĐÂU???.BẠN

NÀO BIẾT TRẢ LỜI GIÚP MÌNH NHA

b) \(x^3+2x^2-6x-27\)

\(=\left(x-3\right)\left(x^3+3x+9\right)+2x\left(x-3\right)\)

\(=\left(x-3\right)\left(x^3+3x+9+2x\right)\)

\(=\left(x+3\right)\left(x^3+5x+9\right)\)

a) \(x^3-x^2-5x+125\)

\(=\left(5+x\right)\left(25-5x+x^2\right)-x\left(5+x\right)\)

\(=\left(5+x\right)\left(25-5x+x^2-x\right)\)

\(=\left(5+x\right)\left(25-4x+x^2\right)\)

yx99=30,25-10

yx99=20,25

y=20,25:99

y=0,20(45)

ta thấy 10+16=26

16+26=42

=> số đằng sau bằng tổng của hai số đằng trước cộng lại

ta có 16-10=6

nên số trước 10 là 6

ta có 10-6=4

nên số trước 6 là 4 

ta có 6-4=2

nên số trước 4 là 2

vậy số đầu là 2