a)

\(\left(-11\right).\left(-28\right)+\left(-9\right).13\)

\(=308+\left(-9\right).13\)

\(=308+\left(-117\right)\)

\(=191\)

b)

\(\left(-69\right).\left(-31\right)-\left(-15\right).12\)

\(=\left(-69\right).\left(-31\right)+15.12\)

\(=2139+15.12\)

\(=2139+180\)

\(=2319\)

c)

\(\left[16-\left(-5\right)\right].\left(-7\right)\)

\(=\left[16+5\right].\left(-7\right)\)

\(=21.\left(-7\right)\)

\(=-147\)

d)

\(\left[\left(-4\right).\left(-9\right)-6\right].\left[\left(-12\right)-\left(-7\right)\right]\)

\(=\left[\left(-4\right).\left(-9\right)-6\right].\left[\left(-12\right)+7\right]\)

\(=\left[36-6\right].\left[\left(-12\right)+7\right]\)

\(=30.\left[\left(-12\right)+7\right]\)

\(=30.\left(-5\right)\)

\(=-150\)

giúp với

\(A=\left(\dfrac{1}{2}-\dfrac{1}{3}\right).\left(\dfrac{1}{2}-\dfrac{1}{5}\right).\left(\dfrac{1}{2}-\dfrac{1}{7}\right)...\left(\dfrac{1}{2}-\dfrac{1}{99}\right)\)

\(=\dfrac{1}{2.3}.\dfrac{3}{2.5}.\dfrac{5}{2.7}...\dfrac{97}{2.99}=\dfrac{1.3.5.7...97}{2^{49}.3.5.7...99}\) (Có 49 thừa số)

\(=\dfrac{1}{2^{49}.99}\)

- There are a desk, an armchair, two computers and a printer in my father's working room.

- My father has a desk, an armchair, two computers and a printer in his working room.

\(MSC:30\\ \dfrac{3}{5}=\dfrac{3\times6}{5\times6}=\dfrac{18}{30}\\ \dfrac{7}{6}=\dfrac{7\times5}{6\times5}=\dfrac{35}{30}\\ 18< 35\\ =>\dfrac{3}{5}< \dfrac{7}{6}\)

\(\dfrac{3}{5}< 1< \dfrac{7}{6}\)

my / living / next / room / room / is / to / the / but / far / bathroom / from / the.
=> Answer:
The living room is next to my room but far from the bathroom.
HOẶC
The living room is next to the bathroom but far from my room.

#hoctot
 

KO BIẾT

\(\left(x-3\right)\left(x^2-2\right)-2\left(x-3\right)=0\\ =>\left(x-3\right)\left(x^2-2-2\right)=0\\ =>\left(x-3\right)\left(x^2-4\right)=0\\ \Rightarrow\left[{}\begin{matrix}x-3=0\\x^2-4=0\end{matrix}\right.=>\left[{}\begin{matrix}x=3\\x^2=4\end{matrix}\right.\\ =>\left[{}\begin{matrix}x=3\\x=2\\x=-2\end{matrix}\right.\)

U = 1 . 2 + 1 . 3 + 2 . 2 + 2 . 3 + ... + 99 . 2 + 99 . 3

    = ( 1 . 2 + 2 . 2 + ... + 99 . 2 ) + ( 1 . 3 + 2 . 3 + ... + 99 . 3 )

    = 2( 1 + 2 + ... + 99 ) + 3( 1 + 2 + ... + 99 )

    = 5( 1 + 2 + ... + 99 ) 

Đặt A = 1 + 2 + ... + 99

Số số hạng của tổng A là ( 99 - 1 ) : 1 + 1 = 99 ( số hạng )

A = ( 99 + 1 ) . 99 : 2 = 4950

U = 5 . 4950 = 24750

Vậy U = 24750