x * 6,5  = 20 - 3,5 

x * 6,5 = 16 ,5 

x = 16 ,5 : 6,5 

x = 2 ,538461...

k nha

X = 2 nhé

6.5 + 3.5 = 10

20 : 10 = 2

X x 6,5 + 3,5 = 20

X x 6,5 = 16,5

X = 16,5 : 6,5

X = 2,5384....

\(x=\frac{10^2.5^3.15^6}{3^6.5^{10}}=\frac{\left(2.5\right)^2.\left(3.5\right)^6}{3^6.5^7}=\frac{2^2.5^2.3^6.5^6}{3^6.5^7}=2^2.5=20\)

Vậy x = 20

@Nguyễn Huy Tú bạn có thể viết rõ cách làm có dc ko?

\(5^{x+1}+6.5^{x+1}=875\)

\(\Rightarrow5^{x+1}.\left(1+6\right)=875\)

\(\Rightarrow5^{x+1}.7=875\)

\(\Rightarrow5^{x+1}=875:7=125\)

\(\Rightarrow5^{x+1}=5^3\)

\(\Rightarrow x+1=3\)

\(\Rightarrow x=3-1=2\)

1/x : 0,2 + 2/x : 0,25  =6,5

1/x : 1/5 + 2/x : 1/4=6,5

1/x  x  5/1 + 2/x x 4/1 = 6,5

5/x+8/x = 6,5

13/x=6,5

13:x=6,5

x=13:6,5

x=2

y=100.7

y=100.7

y:0,04 + y x 3/2-y x 6,5 = 2014

y x 25 + y x 1,5 -y x 6,5=2014

y(25+1,5-6,5) =2014

20 x y=2014

Vậy y = 2014/20= 100,7

\(x=\frac{10^2.5^3.15^6}{3^6.5^{10}}=\frac{\left(2.5\right)^2.5^3.\left(3.5\right)^6}{3^6.5^{10}}=\frac{2^2.5^2.5^3.3^6.5^6}{3^6.5^{10}}=\frac{2^2.5^{11}.3^6}{3^6.5^{10}}=2^2.5=4.5=20\)

Vậy x=20.

Câu 1 : \(0,36\times630+0,6\times36\times6+3,6\)

\(=0,36\times10\times63+0,6\times6\times36+3,6\)

\(=3,6\times63+3,6\times36+3,6\)

\(=3,6\times\left(63+36+1\right)\)

\(=3,6\times100\)

\(=360\)

 Câu 2 :\(3,5\times20,2+6,5\times27,9+3,5\times2,2-6,5\times5,5\)

\(=3,5\times\left(20,2+2,2\right)+6,5\times\left(27,9-5,5\right)\)

\(=3,5\times22,4+6,5\times22,4\)

\(=22,4\times\left(3,5+6,5\right)\)

\(=22,4\times10\)

\(=224\)

Đặt \(A=\frac{1}{2.3}+\frac{1}{6.5}+\frac{1}{10.7}+...+\frac{1}{198.101}.\)

\(2A=\frac{2}{2.3}+\frac{2}{6.5}+\frac{2}{10.7}+...+\frac{2}{198.101}\)

\(=\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+...+\frac{1}{99.101}\)

\(4A=\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{99.101}\)

\(=\frac{1}{1}-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{99}-\frac{1}{101}\)

\(=\frac{1}{1}-\frac{1}{101}\)\(=\frac{100}{101}\)

\(A=\frac{100}{101}\div4=\frac{25}{101}\)

\(\Rightarrow\frac{25}{101}x=1\)

\(x=1\div\frac{25}{101}=\frac{101}{25}\)

101phan 25

c) \(\left|x\right|=3,5\Rightarrow\left[{}\begin{matrix}x=3,5\\x=-3,5\end{matrix}\right.\)

d) \(\left|x\right|=-2,7\Rightarrow x\in\varnothing\) 

l) \(\left|x+\dfrac{3}{4}\right|-5=-2\Rightarrow\left|x+\dfrac{3}{4}\right|=3\)

\(\Rightarrow\left[{}\begin{matrix}x+\dfrac{3}{4}=3\\x+\dfrac{3}{4}=-3\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=3-\dfrac{3}{4}\\x=-3-\dfrac{3}{4}\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{9}{4}\\x=\dfrac{15}{4}\end{matrix}\right.\)

Đính chính câu l \(x=-\dfrac{15}{4}\) không phải \(x=\dfrac{15}{4}\)

c) x = 3,5 hoặc -3,5

d) x = -2,7

e) x = -1,27

f) x = 0

g) x = -2

h) x = 0

l) x = 9/4

   x = -15/4