\(x:0,25-x=15,6\)

\(x:\dfrac{1}{4}-x=15,6\)

\(x\text{×}4-x\text{×}1=15,6\)

\(x\text{×}\left(4-1\right)=15,6\)

\(x\text{×}3=15,6\)

\(x=15,6:3\)

\(x=5,2\)

x :0,25 -x=15,6

X x4 -x =15,6

X -1 x4 =15,6

X -4 =15,6 

X=15,6+4

X=19,6

x:0,25-x=15,6

x.4-x=15,6

x.(4-1)=15,6

x.3=15,6

   x=15,6:3

   x=5,2

\(9,65\times0,4\times0,25\)

\(=\)\(9,65\times\left(0,4\times0,25\right)\)

\(=\)\(9,65\times0,1\)

\(=\)\(0,965\)

\(0,25\times40\times9,84\)

\(=\)\(\left(0,25\times40\right)\times9,84\)

\(=\)\(10\times9,84\)

\(=\)\(98,4\)

\(\sqrt{x-2\sqrt{x-1}}=\sqrt{x-1}-1\left(đk:x\ge1\right)\)

\(< =>\sqrt{x-2\sqrt{x-1}}^2=\left(\sqrt{x-1}-1\right)^2\)

\(< =>x-2\sqrt{x-1}=x-1+1-2\sqrt{x-1}\)

\(< =>x-2\sqrt{x-1}+2\sqrt{x-1}=x< =>x=x\)

Vậy phương trình trên thỏa mãn với mọi \(x\ge1\)

ĐKXĐ : \(x\ge1\)

Bình phương 2 vế lên ta có :

\(x-2\sqrt{x-1}=\left(\sqrt{x-1}-1\right)^2\)

\(\Leftrightarrow x-2\sqrt{x-1}=x-1-2\sqrt{x-1}+1\)

\(\Leftrightarrow x-2\sqrt{x-1}=x-2\sqrt{x-1}\)

\(\Leftrightarrow0x=0\)( luôn đúng với mọi \(x\ge1\))

Vậy ...............

\(\text{X : 0,25 - X = 15,6}\)

\(x:\left(0,25-1\right)=15,6\)

\(x.\left(\frac{-3}{4}\right)=\frac{78}{5}\)

\(x=\frac{78}{5}:\left(\frac{-3}{4}\right)\)

\(x=-20,8\)

chúc bạn học tốt

\(x\div0,25-x=15,6\)

\(\Leftrightarrow\)\(x\div\frac{1}{4}-x=15,6\)

\(\Leftrightarrow\)\(x\times4-x=15,6\)

\(\Leftrightarrow\)\(x\times\left(4-1\right)=15,6\)

\(\Leftrightarrow\)\(x\times3=15,6\)

\(\Leftrightarrow\)\(x=15,6\div3\)

\(\Leftrightarrow\)\(x=5,2\)

Ta tính thêm dãy từ $1$đến $9$vào dãy số ban đầu. 

Tổng của dãy số sau khi thêm là: $4905+\left(1+2+...+9\right)=4905+\genfrac{}{}{0ex}{}{9\times \left(9+1\right)}{2}=4950$.

Từ $1$đến $x$có $x$số hạng. 

Tổng của dãy đó là $\left(x+1\right)\times x÷2$

Suy ra $\left(x+1\right)\times x÷2=4950$

$\left(x+1\right)\times x=4950\times 2=9900=100\times 99$

Suy ra $x=99$.

x:0,25-x=15,6

x.4-x=15,6

x.(4-1)=15,6

x.3=15,6

   x=15,6:3

   x=5,2

\(x:0,25-x=15,6\)

\(\Leftrightarrow4x-x=15,6\)

\(\Leftrightarrow x\left(4-1\right)=15,6\)

\(\Leftrightarrow3x=15,6\)

\(\Leftrightarrow x=5,2\)

\(x\div0,25-x=15,6\)

\(\Rightarrow\)\(x\div\frac{1}{4}-x=15,6\)

\(\Rightarrow\)\(x\times4-x=15,6\)

\(\Rightarrow\)\(x\times\left(4-1\right)=15,6\)

\(\Rightarrow\)\(x\times3=15,6\)

\(\Rightarrow\)\(x=15,6\div3\)

\(\Rightarrow\)\(x=5,2\)

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