2, 

a) \(315-\left(135-x\right)=215\)

\(\Rightarrow135-x=315-215\)

\(\Rightarrow135-x=100\)

\(\Rightarrow x=135-100\)

\(\Rightarrow x=35\)

b) \(x-320:32=25\cdot16\)

\(\Rightarrow x-10=5^2\cdot4^2\)

\(\Rightarrow x-10=20^2\)

\(\Rightarrow x-10=400\)

\(\Rightarrow x=410\)

c) \(3\cdot x-2018:2=23\)

\(=3\cdot x-1009=23\)

\(\Rightarrow3\cdot x=1032\)

\(\Rightarrow x=1032:3\)

\(\Rightarrow x=344\)

d) \(280-9\cdot x-x=80\)

\(\Rightarrow280-x\cdot\left(9+1\right)=80\)

\(\Rightarrow280-10\cdot x=80\)

\(\Rightarrow10\cdot x=280-80\)

\(\Rightarrow10\cdot x=200\)

\(\Rightarrow x=20\)

e) \(38\cdot x-12\cdot x-x\cdot16=40\)

\(\Rightarrow x\cdot\left(38-12-16\right)=40\)

\(\Rightarrow x\cdot10=40\)

\(\Rightarrow x=40:10\)

\(\Rightarrow x=4\)

a) \(\dfrac{27^3\cdot11+9^5\cdot5}{3^9\cdot2^4}\)

\(=\dfrac{3^9\cdot11+3^{10}\cdot5}{3^9\cdot2^4}\)

\(=\dfrac{3^9\cdot\left(11+3\cdot5\right)}{3^9\cdot2^4}\)

\(=\dfrac{11+15}{16}\)

\(=\dfrac{26}{16}\)

\(=\dfrac{13}{8}\)

b) \(\dfrac{5^8+2^2\cdot25^4+2^3\cdot125^3-15^4\cdot5^4}{4^2\cdot625^2}\)

\(=\dfrac{5^8+2^2\cdot5^8+2^3\cdot5^9-3^4\cdot5^4\cdot5^4}{2^4\cdot5^8}\)

\(=\dfrac{5^8\cdot\left(1+2^2+2^3\cdot5-3^4\right)}{5^8\cdot2^4}\)

\(=\dfrac{1+4+40-81}{16}\)

\(=\dfrac{-36}{16}\)

\(=\dfrac{-9}{4}\)

c) \(\dfrac{4^5\cdot9^4-2\cdot6^9}{2^{10}\cdot3^8+6^8\cdot20}\)

\(=\dfrac{2^{10}\cdot3^8-2\cdot2^9\cdot3^9}{2^{10}\cdot3^8+2^{10}\cdot3^8\cdot5}\)

\(=\dfrac{2^{10}\cdot3^8\cdot\left(1-3\right)}{2^{10}\cdot3^8\cdot\left(1+5\right)}\)

\(=\dfrac{-2}{6}\)

\(=-\dfrac{1}{3}\)

Đáy lớn dài bao nhiêu ?

Số con mèo có trong nhà em là:

\(3-2=1\) (con mèo)

Đáp số: 1 con mèo

Số lượng số hạng:

\(\left(299-1\right):1+1=299\) (số hạng)

Tổng S là:
\(\left(299+1\right)\cdot299:2=44850\)

\(\left(2x-3\right)^2-\left(x+5\right)\left(4x-1\right)=-9\)

\(\Leftrightarrow4x^2-12x+9-4x^2+x-20x+5=-9\)

\(\Leftrightarrow-31x+14=-9\)

\(\Leftrightarrow-31x=-23\)

\(\Leftrightarrow x=\dfrac{-23}{-31}\)

\(\Leftrightarrow x=\dfrac{23}{31}\)

1) \(9\cdot9\cdot9\cdot9\cdot3\cdot3\)

\(=3\cdot3\cdot3\cdot3\cdot3\cdot3\cdot3\cdot3\cdot3\cdot3\)

\(=3^{10}\)

2) \(8\cdot2\cdot2\cdot2\cdot16\cdot4\)

\(=2\cdot2\cdot2\cdot2\cdot2\cdot2\cdot2\cdot2\cdot2\cdot2\cdot2\cdot2\)

\(=2^{12}\)

3) \(3\cdot3\cdot3\cdot3\cdot5\cdot5\cdot5\cdot5\)

\(=3^4\cdot5^4\)

4) \(25\cdot25\cdot25\cdot5\)

\(=5\cdot5\cdot5\cdot5\cdot5\cdot5\cdot5\)

\(=5^7\)

5) \(7\cdot49\cdot7\cdot7\cdot7\)

\(=7\cdot7\cdot7\cdot7\cdot7\cdot7\)

\(=7^6\)

6) \(8\cdot64\cdot8\cdot64\)

\(=2\cdot2\cdot2\cdot2\cdot2\cdot2\cdot2\cdot2\cdot2\cdot2\cdot2\cdot2\cdot2\cdot2\cdot2\cdot2\cdot2\cdot2\)

\(=2^{18}\)

7) \(2\cdot2\cdot2\cdot2\cdot2\cdot2\cdot4\)

\(=2\cdot2\cdot2\cdot2\cdot2\cdot2\cdot2\cdot2\)

\(=2^8\)

\(\left(2x-5\right)^2=\left(x-\dfrac{5}{2}\right)^2\)

\(\Leftrightarrow2x-5=x-\dfrac{5}{2}\)

\(\Leftrightarrow2x-x=-\dfrac{5}{2}+5\)

\(\Leftrightarrow x=\dfrac{5}{2}\)

\(2\times3\times5+25\times8\times4+70+4\times2\times25\)

\(=15\times2+100\times8+70+100\times2\)

\(=30+800+70+200\)

\(=\left(30+70\right)+\left(800+200\right)\)

\(=100+100\times10\)

\(=100+1000\)

\(=1100\)