a) \(5x-65=5.3^2 \\ 5x-65=45\\5x=45+65\\5x=110\\x=22\)

b) \(200-(2x+6)=4^3\\2x+6=200-4^3\\2x+6=136\\2x=130\\x=65\)

c) \(2(x-51)=2.2^3+20\\2(x-51)=16+20\\2(x-51)=36\\x-51=18\\x=51+18=69\)

d) \(135-5(x+4)=35\\5(x+4)=135-45\\5(x-4)=90\\x-4=18\\x=18+4=22\)

e) \((2x-4)(15-3x)=0\\2(x-2).3(5-x)=0\\(x-2)(5-x)=0\\ \left[ \begin{array}{l}x-2=0\\5-x=0\end{array} \right. \\ \left[ \begin{array}{l}x=2\\x=5\end{array} \right.\)

f) \(2^{x+1} . 2^{2014}=2^{2016} \\ (2^{x+1} . 2^{2014}):2^{2014}=2^{2016} :2^{2014} \\ 2^{x=1}=2^{2016-2014} \\2^{x+1}=2^2\\x+1=2\\x=1\)

g) \(15+(x-1)^3=43\\(x-1)^3=15-42\\(x-1)^3=-27\\(x-1)^3=(-3)^3\\x-1=-3\\x=-2\)

h) \(15-x=17+(-9)\\15-x=17-9\\15-x=8\\x=15-8\\x=7\)

i) \(|x-5|=|-7|+|-4|\\|x-5|=7+4\\|x-5|=11\\ \left[ \begin{array}{l}x-5=11\\x-5=-11\end{array} \right. \\ \left[ \begin{array}{l}x=16\\x=-6\end{array} \right.\)

k) \(|x-3|-12=-9+|-7|\\|x-3|-12=-9+7\\|x-3|-12=-2\\|x-3|=10 \\ \left[ \begin{array}{l}x-3=10\\x-3=-10\end{array} \right. \\ \left[ \begin{array}{l}x=13\\x=-7\end{array} \right.\)

ĐK: \(\begin{cases}x≥1\\x≥2\\x≥3\end{cases} \Leftrightarrow x≥3\)

\(\sqrt{x-1}-\sqrt{x-2}=\sqrt{x-3} \\ \Leftrightarrow \sqrt{x-1}=\sqrt{x-3}+\sqrt{x-2} \\ \Leftrightarrow x-1= x-3+x-2+2\sqrt{(x-2)(x-3)} \\\Leftrightarrow -x+4=2\sqrt{(x-2)(x-3)} \\ \Leftrightarrow x^2-8x+16=4(x-2)(x-3) (ĐK: 3≤x≤4) \\ \Leftrightarrow x^2-8x+16=4x^2-20x+24\\\Leftrightarrow3x^2-12x+8=0 \\ \Leftrightarrow x = \dfrac{6 \pm 2\sqrt3}{3}\)

Vậy \(x=\dfrac{6+2\sqrt3}{3}\).

\(x \in U(20) \Rightarrow x \in {1;2;4;5;10;20} \)

Mà \(0 < x < 1 0\)

\(\Rightarrow x \in {1;2;4;5;10} \).

.

\(x \in U(30) \Rightarrow x \in {1;3;5;6;10;15;30}\)

Mà \(5 < x ≤ 15\)

\( \Rightarrow x \in {6;10;15}\).

\(-|-5|+(-19)+18+|11-4|-57\\=-5-19+18+7-57\\=(18-19-5)-(57-7)\\=-6-50\\=-56\)

\(126+(-20)+|124|-(-320)-|-150|\\=126-20+124+320+125\\=(320-20)+124+125+126\\=300+375\\=675\)

\(x^2-2x+1=0\\ \Leftrightarrow x^2-2.x.1 +1^2=0 \\ \Leftrightarrow (x-1)^2=0 \\\Leftrightarrow x-1=0 \\ \Leftrightarrow x=1\)

Vậy \(x=1\).

1. Yes, I do.

2. Studying, reading books, playing with friends are all activities that I do at school.

3. My house has 2 floors, and my room is on the second. When u go upstairs, turn right, u will see 2 rooms, the first one is mine. It's not so big but it has everything I need: my clothes, books, my tiny bed, playing corners,...That's all !!

4. Actually, I don't remember my first day at school...

⇒ a. used to be.

⇒ a. inquisitive : tọc mạch