a: =25x10=250

b: =34x6=204

a =25 x 10=250

b =34x(11-5)=34x6=204

a. 25 x 10 =250

 C2: 25 x4 + 25 x 6 = 250

b. 374 - 170 =204

 C2 : 34 x ( 11 -5 ) = 34 x 6 = 204

Áp dụng tính chất của dãy tỷ số bằng nhau

\(\frac{3x-1}{40-5x}=\frac{25-3x}{4x-34}=\frac{\left(3x-1\right)+\left(25x-3x\right)}{\left(40-5x\right)+\left(5x-34\right)}=4\)

\(\Rightarrow\frac{3x-1}{40-5x}=4\)

\(\Rightarrow3x-1=3\left(40-5x\right)\)

\(\Rightarrow3x-1=160-20x\)

\(\Rightarrow23x=161\)

\(\Rightarrow x=161:23\)

\(\Rightarrow x=7\)

`a, = 5^3 xx 3^3 = 15^3`

`b, = 12^3 xx 4^3 = 48^3`

`c, = 625^3 xx 8^3 = 5000^3`

`d, = 625 ^3 xx 125^3 = 78125^3`

`e, = 5^20 : 5^14 = 5^6`

1,\(125\cdot27=5^3\cdot3^3=\left(5\cdot3\right)^3=15^3\)

2, \(12^3\cdot64=12^3\cdot4^3=\left(12\cdot4\right)^3=48^3\)

3, \(25^6\cdot8^3=\left(5^2\right)^6\cdot\left(2^3\right)^3=5^8\cdot2^9\)

4, \(25^6\cdot125^3=\left(5^2\right)^3\cdot\left(5^3\right)^3=5^6\cdot5^9=5^{15}\)

5,\(625^5:25^7=\left(5^4\right)^5:\left(5^2\right)^7=5^{20}:5^{14}=5^6\)

a: \(=\dfrac{18}{51}\cdot\dfrac{34}{9}\cdot\dfrac{17}{18}=\dfrac{17}{51}\cdot\dfrac{34}{9}=\dfrac{1}{3}\cdot\dfrac{34}{9}=\dfrac{34}{27}\)

b: \(=\dfrac{21}{32}\cdot\dfrac{4}{7}\cdot25\cdot\dfrac{4}{5}=\dfrac{21}{7}\cdot\dfrac{4}{32}\cdot20=60\cdot\dfrac{1}{8}=\dfrac{15}{2}\)

\(\left(3-x\right)\left(3+x\right)+\left(x-5\right)^2\\ =9-x^2+x^2-10x+25\\ =34-10x\)

Đáp án là D

34 - (25 + 34) = x - (25 - 9)

34 - 25 - 34 = x - 16

34 - 34 - 25 = x - 16

-25 = x - 16

-25 + 16 = x

-(25 - 16) = x

-9 = x