Question

giúp em với ạ , ai bt là câu nào thì giúp em câu đó với ạ :((

Answer 1

b) \(\overline{2,x\left(y\right)}=2+\overline{0,x\left(y\right)}=2+\dfrac{\overline{xy}}{99}=2+\dfrac{10x+y}{99}\)

\(\overline{1,y\left(x\right)}=1+\overline{0,y\left(x\right)}=1+\dfrac{\overline{yx}}{99}=1+\dfrac{10y+x}{99}\)

\(1,2\left(6\right)=1+0,2\left(6\right)=1+\dfrac{26-2}{90}=1+\dfrac{24}{90}=1+\dfrac{4}{15}=\dfrac{19}{15}\)

\(\overline{2,x\left(y\right)}-\overline{1,y\left(x\right)}=1,2\left(6\right)\)

\(2+\dfrac{10x+y}{99}-1-\dfrac{10y+x}{99}=\dfrac{19}{15}\)

\(1+\dfrac{10x+y-10y-x}{99}=\dfrac{19}{15}\)

\(\dfrac{9x-9y}{99}=\dfrac{19}{15}-1\)

\(\dfrac{9\left(x-y\right)}{99}=\dfrac{4}{15}\)

\(\dfrac{x-y}{11}=\dfrac{4}{15}\)

\(x-y=\dfrac{44}{15}\)

mà \(x+y=7\)

\(\Rightarrow x=\dfrac{\dfrac{44}{15}+7}{2}=\dfrac{149}{30}\)

\(\Rightarrow y=7-\dfrac{149}{30}=\dfrac{61}{30}\)

Vậy \(\left(x;y\right)=\left(\dfrac{149}{30};\dfrac{61}{30}\right)\)

 

Answer 2

a.

\(1:0,\overline{ab}=a+b-c\Rightarrow\dfrac{100}{\overline{ab}}=a+b-c\)

\(\Rightarrow100\) chia hết cho \(\overline{ab}\), mà \(\overline{ab}\) là STN có 2 chữ số nên \(\overline{ab}\) có thể là 10, 20, 25, 50

- Nếu \(\overline{ab}=10\Rightarrow\left\{{}\begin{matrix}a=1\\b=0\end{matrix}\right.\) \(\Rightarrow\dfrac{100}{10}=1+0-c\Rightarrow c=-9\) (loại)

- Nếu \(\overline{ab}=20\Rightarrow a=2;b=0\Rightarrow\dfrac{100}{20}=2+0-c\Rightarrow c=-3\) (loại)

- Nếu \(\overline{ab}=25\Rightarrow a=2;b=5\Rightarrow\dfrac{100}{25}=2+5-c\Rightarrow c=3\) (nhận)

- Nếu \(\overline{ab}=50\Rightarrow a=5;b=0\Rightarrow\dfrac{100}{50}=5+0-c\Rightarrow c=3\) (nhận)

Vậy có 2 phép tính thỏa mãn:

\(1:0,25=2+5-3\) hoặc \(1:0,50=5+0-3\)

 

Answer 3

b.

\(\overline{2,x\left(y\right)}-\overline{1,y\left(x\right)}=1,2\left(6\right)\)

\(\Rightarrow2+\dfrac{x}{10}+\dfrac{y}{90}-\left(1+\dfrac{y}{10}+\dfrac{x}{90}\right)=1+\dfrac{2}{10}+\dfrac{6}{90}\)

\(\Rightarrow\dfrac{4}{45}x-\dfrac{4}{45}y=\dfrac{4}{15}\)

\(\Rightarrow\dfrac{4}{45}\left(x-y\right)=\dfrac{4}{15}\)

\(\Rightarrow x-y=3\)

\(\Rightarrow x=y+3\)

Thay vào \(x+y=7\)

\(\Rightarrow y+3+y=7\Rightarrow y=2\)

\(\Rightarrow x=2+3=5\)

Vậy phép tính là: \(2,5\left(2\right)-1,2\left(5\right)=1,2\left(6\right)\)