29: Ta có: \(\dfrac{1}{\sqrt{7}+\sqrt{5}}+\dfrac{2}{1-\sqrt{7}}\)

\(=\dfrac{\sqrt{7}-\sqrt{5}}{2}-\dfrac{2\sqrt{7}-2}{6}\)

\(=\dfrac{3\sqrt{7}-3\sqrt{5}-2\sqrt{7}+2}{6}\)

\(=\dfrac{-3\sqrt{5}-2}{6}\)

30: Ta có: \(\dfrac{4}{1-\sqrt{3}}+\dfrac{\sqrt{3}-1}{\sqrt{3}+1}\)

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

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

31: Ta có: \(\dfrac{1}{\sqrt{2}-\sqrt{3}}-\dfrac{3}{\sqrt{18}+2\sqrt{3}}\)

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

\(=-\sqrt{3}-\sqrt{2}-\dfrac{9\sqrt{2}-6\sqrt{3}}{6}\)

\(=\dfrac{-6\sqrt{3}-6\sqrt{2}-9\sqrt{2}+6\sqrt{3}}{6}=\dfrac{-15\sqrt{2}}{6}\)

\(=\dfrac{-5\sqrt{2}}{2}\)

29.

\(=\frac{\sqrt{7}-\sqrt{5}}{(\sqrt{7}-\sqrt{5})(\sqrt{7}+\sqrt{5})}+\frac{2(1+\sqrt{7})}{(1-\sqrt{7})(1+\sqrt{7})}\)

\(=\frac{\sqrt{7}-\sqrt{5}}{7-5}+\frac{2(1+\sqrt{7})}{1-7}=\frac{\sqrt{7}-\sqrt{5}}{2}-\frac{1+\sqrt{7}}{3}=\frac{\sqrt{7}-3\sqrt{5}-2}{6}\)

30.

\(=\frac{4(1+\sqrt{3})}{(1-\sqrt{3})(1+\sqrt{3})}+\frac{(\sqrt{3}-1)^2}{(\sqrt{3}+1)(\sqrt{3}-1)}=\frac{4(1+\sqrt{3})}{1-3}+\frac{4-2\sqrt{3}}{3-1}\)

\(=\frac{4(1+\sqrt{3})}{-2}+\frac{4-2\sqrt{3}}{2}=-2(1+\sqrt{3})+2-\sqrt{3}=-3\sqrt{3}\)

?????

cho mình xin đề bài với ạ

1: does not/doesn't
2:did not/didn't
3:are not/aren't
4:are not/aren't
5:does not/doesn't
mình cũng ko chắc vài câu vì ko có từ ngữ cụ thể ạ

\(=8\cdot25-72:9=200-8=192\)

= 8 . 25 - 72 : 9

= 200 - 8

= 192

2^3.25-72:3^2

=8.25-72:9

=192

3.

\(y=\dfrac{1-sin^24x}{5}=\dfrac{cos^24x}{5}\)

\(cos4x\in\left[-1;1\right]\Rightarrow cos^24x\in\left[0;1\right]\Rightarrow y\in\left[0;\dfrac{1}{5}\right]\Rightarrow\left\{{}\begin{matrix}y_{min}=0\\y_{max}=\dfrac{1}{5}\end{matrix}\right.\)

6.

\(y=sinx+cosx+2=\sqrt{2}sin\left(x+\dfrac{\pi}{4}\right)+2\)

\(sin\left(x+\dfrac{\pi}{4}\right)\in\left[-1;1\right]\Rightarrow y=\sqrt{2}sin\left(x+\dfrac{\pi}{4}\right)+2\in\left[-\sqrt{2}+2;\sqrt{2}+2\right]\)

\(\Rightarrow y_{min}=-\sqrt{2}+2\)

\(y_{max}=\sqrt{2}+2\)

1.

\(sin2x\in\left[-1;1\right]\Rightarrow y=3-2sin2x\in\left[1;5\right]\)

\(\Rightarrow\left\{{}\begin{matrix}y_{min}=1\\y_{max}=5\end{matrix}\right.\)

Trả lời :

3³ . ( - 3 )⁸ = ( -3 )³⁺⁸ = ( - 3 ) ¹¹

#Chuk bn hok ttoos :3

Sai thì đừng t i c k sai nhé :)

-Nhớ đeí

\(a^{-n}=\frac{1}{a^n}\left(a\ne0;n\inℤ\right)\)

@ Cậu chủ fb @

Số âm mũ chẵn chính bằng số dương mũ chẵn:

\(\left(-3\right)^8=3^8\)

Nên \(3^3.\left(-3\right)^8=3^3.3^8=3^{3+8}=3^{11}\)