\(a,\sqrt{\sqrt{5}-\sqrt{3-\sqrt{29-12\sqrt{5}}}}\\ =\sqrt{\sqrt{5}-\sqrt{3-\left(2\sqrt{5}-3\right)}}\\ =\sqrt{\sqrt{5}-\sqrt{6-2\sqrt{5}}}\\ =\sqrt{\sqrt{5}-\left(\sqrt{5}-1\right)}\\ =\sqrt{1}=1\)

\(b,\sqrt{13+30\sqrt{2+\sqrt{9+4\sqrt{2}}}}\\ =\sqrt{13+30\sqrt{2+\left(2\sqrt{2}+1\right)}}\\ =\sqrt{13+30\sqrt{3+2\sqrt{2}}}\\ =\sqrt{13+30\left(\sqrt{2}+1\right)}\\ =\sqrt{43+30\sqrt{2}}\\ =5+3\sqrt{2}\)

\(c,\sqrt{1+\sqrt{3+\sqrt{13+4\sqrt{3}}}}+\sqrt{1-\sqrt{3-\sqrt{13-4\sqrt{3}}}}\\ =\sqrt{1+\sqrt{3+\left(2\sqrt{3}+1\right)}}+\sqrt{1-\sqrt{3-\left(2\sqrt{3}-1\right)}}\\ =\sqrt{1+\sqrt{4+2\sqrt{3}}}+\sqrt{1-\sqrt{4-2\sqrt{3}}}\\ =\sqrt{1+\left(\sqrt{3}+1\right)}+\sqrt{1-\left(\sqrt{3}-1\right)}\\ =\sqrt{2+\sqrt{3}}+\sqrt{2-\sqrt{3}}\)

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

\(A^2=4+2\sqrt{\left(2+\sqrt{3}\right)\left(2-\sqrt{3}\right)}=4+2=6\\ A=\sqrt{6}\)

Vậy gt biểu thức là \(\sqrt{6}\)

\(d,\sqrt{5-\sqrt{13+4\sqrt{3}}}+\sqrt{3+\sqrt{13+4\sqrt{3}}}\\ =\sqrt{5-\left(2\sqrt{3}+1\right)}+\sqrt{3+\left(2\sqrt{3}+1\right)}\\ =\sqrt{4-2\sqrt{3}}+\sqrt{4+2\sqrt{3}}\\ =\sqrt{3}-1+\sqrt{3}+1=2\sqrt{3}\)

\(4,\)

\(A=\sqrt{2-\sqrt{3}}+\sqrt{2+\sqrt{3}}\\ A^2=2-\sqrt{3}+2+\sqrt{3}+2\sqrt{\left(2-\sqrt{3}\right)\left(2+\sqrt{3}\right)}\\ A^2=4+2=6\\ A=\sqrt{6}\\ B=\sqrt{4-\sqrt{7}}-\sqrt{4+\sqrt{7}}\\ B^2=4-\sqrt{7}+4+\sqrt{7}-2\sqrt{\left(4-\sqrt{7}\right)\left(4+\sqrt{7}\right)}\\ B^2=8-2\sqrt{9}=8-6=2\\ B=\sqrt{2}\)

\(5,\\ a,\sqrt{5+2\sqrt{6}}-\sqrt{5-2\sqrt{6}}\\ =\sqrt{\left(\sqrt{2}+\sqrt{3}\right)^2}-\sqrt{\left(\sqrt{3}-\sqrt{2}\right)^2}\\ =\sqrt{2}+\sqrt{3}-\sqrt{3}+\sqrt{2}=2\sqrt{2}\\ b,\sqrt{7-2\sqrt{10}}-\sqrt{7+2\sqrt{10}}\\ =\left(\sqrt{5}-\sqrt{2}\right)-\left(\sqrt{2}+\sqrt{5}\right)=-2\sqrt{2}\\ c,\sqrt{24+8\sqrt{5}}+\sqrt{9-4\sqrt{5}}\\ =\left(2\sqrt{5}-2\right)+\left(\sqrt{5}-2\right)\\ =3\sqrt{5}\\ d,\sqrt{17-12\sqrt{2}}+\sqrt{9+4\sqrt{2}}\\ =\left(3-2\sqrt{2}\right)+\left(2\sqrt{2}+1\right)\\ =4\)

Giúp em với 

16, a

17, a

18, d

19, a

20, b

21, c

17 B: (động vật hoang dã)

19 A:(khí hậu mưa)

20 B(bị động và expect+to-v)

21 C(động lực)

16 A

17 A

17 D

19 A

20 B

21 C

Câu 1:

\(\left(4x+3\right)\left(3x^2+x-2\right)\left(2x^2-3x-5\right)=0\\ \Leftrightarrow\left(4x+3\right)\left(3x-2\right)\left(x+1\right)\left(2x-5\right)\left(x+1\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{3}{4}\\x=-1\\x=\dfrac{2}{3}\\x=\dfrac{5}{2}\end{matrix}\right.\\ \Leftrightarrow A=\left\{-1;-\dfrac{3}{4};\dfrac{2}{3};\dfrac{5}{2}\right\}\)

Câu 2:

\(\left(x^2-4\right)\left(x-3\right)=0\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-2\\x=3\end{matrix}\right.\Leftrightarrow A=\left\{-2;2;3\right\}\\ \left|5x\right|-11\le0\Leftrightarrow\left|5x\right|\le11\Leftrightarrow-11\le5x\le11\\ \Leftrightarrow-\dfrac{11}{5}\le x\le\dfrac{11}{5}\\ \Leftrightarrow B=\left[-\dfrac{11}{5};\dfrac{11}{5}\right]\)

\(\Leftrightarrow A\cap B=\left\{-2;2\right\}\\ A\cup B=\left[-\dfrac{11}{5};3\right]\\ A\B=\left\{3\right\}\)

6:

\(2^{225}=\left(2^3\right)^{75}=8^{75}\)

\(3^{150}=\left(3^2\right)^{75}=9^{75}\)

mà 8<9

nên \(2^{225}< 3^{150}\)

4: \(\left|5x+3\right|>=0\forall x\)

=>\(-\left|5x+3\right|< =0\forall x\)

=>\(-\left|5x+3\right|+5< =5\forall x\)

Dấu = xảy ra khi 5x+3=0

=>x=-3/5

1:

\(\left(2x+1\right)^4>=0\)

=>\(\left(2x+1\right)^4+2>=2\)

=>\(M=\dfrac{3}{\left(2x+1\right)^4+2}< =\dfrac{3}{2}\)

Dấu = xảy ra khi 2x+1=0

=>x=-1/2

 \(=>Qthu1=0,2.340000=68000J\)

\(=>Qthu2=2100.0,2.20=8400J\)

\(=>Qtoa=2.4200.25=210000J\)

\(=>Qthu1+Qthu2< Qtoa\)=>đá nóng chảy hoàn toàn

\(=>0,2.2100.20+0,2.340000+0,2.4200.tcb=2.4200\left(25-tcb\right)\)

\(=>tcb=14,5^oC\)

1.she spends 20 minutes to draw a picture

2.Lan is the most creative in the group

3.No one is smaller than him

4.My pen isn't the same than mine

5.Lan is jealous than her

6.My brother no longer raise pets

-chúc bạn thật thông minh!!!!