tacos\(3^x.3^2+2.3^x=33\)

\(\Leftrightarrow3^x.11=33\Leftrightarrow3^x=3\Leftrightarrow x=1\)

A

a)A=\(2\sqrt{3}-8\sqrt{3}+7\sqrt{3}=\sqrt{3}\)

b)B\(=\sqrt{\left(3-\sqrt{5}\right)^2}+\sqrt{\left(2-\sqrt{5}\right)^2}=3-\sqrt{5}+\sqrt{5}-2=1\)

d)\(=\dfrac{\left(5+\sqrt{5}\right)\left(\sqrt{5}-2\right)}{1}+1-\sqrt{5}-\dfrac{11\left(2\sqrt{5}-3\right)}{11}=5\sqrt{5}+5-10-2\sqrt{5}+1-\sqrt{5}-2\sqrt{5}+3=-1\)

\(Pảilà\dfrac{2\left(\sqrt{x}-2\right)}{\left(\sqrt{x}-2\right)x}=\dfrac{2}{x}mớiđúngnhanãytuinhầm\)

Bài 2

a) A\(=\sqrt{\left(\sqrt{7}+1\right)^2}-\sqrt{\left(2+\sqrt{7}\right)^2}=\sqrt{7}+1-2-\sqrt{7}=-1\)

b)B=\(\left(\dfrac{x-4-x+2\sqrt{x}}{x-4}\right).\dfrac{\sqrt{x}+2}{x}=\dfrac{2\left(\sqrt{x}-2\right)}{\left(\sqrt{x}-2\right)\sqrt{x}}=\dfrac{2}{\sqrt{x}}\)

nH2SO4 = VH2SO4 . CM H2SO4= 0,2 . 1 = 0,2mol

PTHH:       2NaOH    +    H2SO4 →  Na2SO4 + H2O

                     2 mol             1 mol     

                    ? mol               0,2mol

m NaOH= n NaOH.MNaOH = 0,4 . (23 + 16 + 1) = 16g

C% = mNaOH : m dd NaOH

=> mdd NaOH = mNaOH : C% = 16 : 20% = 80g

Bài 1

a)\(\Leftrightarrow2\sqrt{x-5}+\sqrt{x-5}-\sqrt{x-5}=4\)    Đk x\(\ge5\)

\(\Leftrightarrow x=9\left(nhận\right)\)

b)\(\sqrt{4x^2-4x+1}=5đkx\ge\dfrac{1}{2}\)

\(\Leftrightarrow\sqrt{\left(2x-1\right)^2}=5\)

\(\Leftrightarrow\left|2x-1\right|=5\)

\(\Leftrightarrow\left[{}\begin{matrix}2x-1=5\\2x-1=-5\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=3\left(nhận\right)\\x=-2\left(loại\right)\end{matrix}\right.\)

vậy S=\(\left\{3\right\}\)

c)\(\sqrt{9x^2+6x+1}=2x-3đkx\ge-\dfrac{1}{3}\)

\(\Leftrightarrow\sqrt{\left(3x+1\right)^2}=2x-3\)

\(\Leftrightarrow\left|3x+1\right|=2x-3\)

\(\Leftrightarrow\left[{}\begin{matrix}3x+1=2x-3\\3x+1=3-2x\end{matrix}\right.\)\(\Leftrightarrow\left[{}\begin{matrix}x=-4\left(loại\right)\\x=\dfrac{2}{5}\left(nhận\right)\end{matrix}\right.\)

Vây S=\(\left\{\dfrac{2}{5}\right\}\)

2)

A=\(4\sqrt{7}+9\sqrt{7}-20\sqrt{7}+3\sqrt{7}=-4\sqrt{7}\)

B=\(\left(3x-2\right)\sqrt{\left(\dfrac{3}{2-3x}\right)^2}=\left(3x-2\right)\left(\dfrac{3}{2x-3}\right)=-3\)