:v lớp 10

D

xem ai thông minh, tinh mắt nhất có thể luận ra toàn bộ đề và giúp mk giải nào!! 

Mình chả thấy gì cả 

Ta có: \(\dfrac{1}{2}\cdot y+\dfrac{2}{3}\cdot y=\dfrac{7}{6}\Rightarrow y\left(\dfrac{1}{2}+\dfrac{2}{3}\right)=\dfrac{7}{6}\Rightarrow\dfrac{7}{6}y=\dfrac{7}{6}\Rightarrow y=\dfrac{7}{6}:\dfrac{7}{6}=1\)

Vậy \(D=\left\{1\right\}\)

1

B. Sai

sai

b)Đặt \(\frac{2x}{3}=\frac{3y}{4}=\frac{4z}{5}=k\)

\(\Rightarrow x=\frac{3k}{2}\)

\(y=\frac{4k}{3}\)

\(z=\frac{5k}{4}\)

\(x+y+z=98\)

\(\Leftrightarrow\frac{3k}{2}+\frac{4k}{3}+\frac{5k}{4}=98\)

\(\frac{18k}{12}+\frac{16k}{12}+\frac{15k}{12}=98\)

\(\frac{18k+16k+15k}{12}=98\)

\(49k=1176\)

\(k=24\)

\(\Rightarrow x=\frac{3k}{2}=\frac{3\cdot24}{2}=\frac{72}{2}=36\)

\(y=\frac{4k}{3}=\frac{4\cdot24}{3}=\frac{96}{3}=32\)

\(z=\frac{5k}{4}=\frac{5\cdot24}{4}=\frac{120}{4}=30\)

Vậy ... (kết luận tự túc)

2 câu sau... unknow

\(\Rightarrow\dfrac{5}{4}-\dfrac{1}{4}x=\dfrac{3}{10}x-\dfrac{2}{5}\)

\(\Rightarrow\dfrac{5}{4}+\dfrac{2}{5}=\dfrac{3}{10}x-\dfrac{1}{4}x\)

\(\Rightarrow\dfrac{33}{20}=\dfrac{11}{20}x\)

\(\Rightarrow x=\dfrac{33}{20}\div\dfrac{11}{20}\)

\(\Rightarrow x=3\)

\(1\dfrac{1}{4}-x\dfrac{1}{4}=x\cdot30\%\cdot\dfrac{2}{5}\)

\(\Leftrightarrow\dfrac{5}{4}-x\dfrac{1}{4}=x\cdot\dfrac{3}{10}-\dfrac{2}{5}\)

\(\Leftrightarrow\dfrac{5}{4}-\dfrac{1}{4}x=\dfrac{3}{10}x-\dfrac{2}{5}\)

\(\Leftrightarrow25-5x=6x-8\)

\(\Leftrightarrow-5x-6x=-8-25\)

\(\Leftrightarrow-11x=-33\)

\(\Leftrightarrow x=3\)

Vậy x = 3

trời 

??? 

a) 4126

b) 615

c) 927

b) 615

c) 927

Bài 1 

a) A : { 12;13;14 }

b) B : { 1;2;3;4;5 }

c) C : { 17;18;19;20;21 }

d) D : { 7;8;9;10 }

Bài 2 

a) M : { 0;1;2;3;4;5;6 }

    M : { x thuộc N / x < 7 }

b) P : { 22;23;24;25 }

    P : { x thuộc N / 21 < x < 26 }