C

C

c

12⁸ : 12⁴ = 12^{8 - 4} = 12⁴

Chọn C

C

b: 12/20+6/18=3/5+1/3=9/15+5/15=14/15

c: 8/12+20/30=2/3+2/3=4/3

d: 10/12+12/36=5/6+2/6=7/6

\(\dfrac{12}{36}=\dfrac{1}{3}\)

5/12 tối giản sẵn r nhé

\(\dfrac{12}{36}\text{=}\dfrac{12:12}{36:12}\text{=}\dfrac{1}{3}\)

\(\dfrac{5}{12}\) là phân số đã được tối giản rồi .

12/36 = 1/3

5/12 = 5/12 ( đây là phân số tối giản r nhé )

\(\dfrac{4}{5}\times\dfrac{4}{3}=\dfrac{16}{15}\)

4/5×4/3=1615

\(=\dfrac{4}{5}\cdot\dfrac{4}{3}=\dfrac{16}{15}\)

6 x + 1 2 + 6 x - 1 2 - 2 1 + 6 x 6 x - 1 = 6 x + 1 2 - 2 1 + 6 x 6 x - 1 + 6 x - 1 2 = 6 x + 1 - 6 x - 1 2 = 6 x + 1 - 6 x + 1 2 = 2 2 = 4

giúp mình nha

Bạn ghi rõ đề ra đi bạn. Khó hiểu quá!

Rút gọn biểu thức: 2323

b, x <

\(\sqrt{17+12\sqrt{2}}-\sqrt{17-12\sqrt{2}}\)

\(=\sqrt{3^2+2\cdot3\cdot2\sqrt{2}+\left(2\sqrt{2}\right)^2}-\sqrt{3^2-2\cdot3\cdot2\sqrt{2}+\left(2\sqrt{2}\right)^2}\)

\(=\sqrt{\left(3+2\sqrt{2}\right)^2}-\sqrt{\left(3-2\sqrt{2}\right)^2}\)

\(=\left|3+2\sqrt{2}\right|-\left|3-2\sqrt{2}\right|\)

\(=3+2\sqrt{2}-3+2\sqrt{2}\)

\(=4\sqrt{2}\)

\(\sqrt{17+12\sqrt{2}}-\sqrt{17-12\sqrt{2}}\)

\(=\sqrt{3^2+2.3.2\sqrt{2}+\left(2\sqrt{2}\right)^2}-\sqrt{3^2-2.3.2\sqrt{2}+\left(2\sqrt{2}\right)^2}\)

\(=\sqrt{\left(3+2\sqrt{2}\right)^2}-\sqrt{\left(3-2\sqrt{2}\right)^2}\)

\(=\left|3+2\sqrt{2}\right|-\left|3-2\sqrt{2}\right|=\left(3+2\sqrt{2}\right)-\left(3-2\sqrt{2}\right)\)

\(=3+2\sqrt{2}-3+2\sqrt{2}=4\sqrt[]{2}\)

`4/7` giữ nguyên

`15/21=(15:3)/(21:3)=5/7`

`----`

`12/36 =(12:12)/(36:12)=1/3`

`5/12` giữ nguyên

`----`

`12/28=(12:4)/(28:4)=3/7`

`6/7` giữ nguyên