Lời giải:

PT $\Leftrightarrow \frac{x+25}{75}+1+\frac{x+30}{70}+1=\frac{x+35}{65}+1+\frac{x+40}{60}+1$

$\Leftrightarrow \frac{x+100}{75}+\frac{x+100}{70}=\frac{x+100}{65}+\frac{x+100}{60}$
$\Leftrightarrow (x+100)(\frac{1}{75}+\frac{1}{70}-\frac{1}{65}-\frac{1}{60})=0$

Dễ thấy $\frac{1}{75}+\frac{1}{70}-\frac{1}{65}-\frac{1}{60}<0$

$\Rightarrow x+100=0$

$\Leftrightarrow x=-100$ (tm)

có sai đầu bài ko (x+36)/70 í

Ta có:\(\frac{x+25}{75}+\frac{x+36}{70}=\frac{x+35}{65}+\frac{x+40}{60}\)
⟺\(\frac{x+25}{75}+1+\frac{x+36}{70}+1=\frac{x+35}{65}+1+\frac{x+40}{60}+1\)

⟺\(\frac{x+100}{75}+\frac{x+100}{70}-\frac{x+100}{65}-\frac{x+100}{60}=0\)

⟺(x+100)(....)=0

⟺x=-100(vì cái trng ngoặc luôn khác 0)

đề bị nhầm mất một dấu pk bạn

mk nghĩ là vậy 

nhẩm bình phương tận cùng là 5:

(10a+5)²=100a.(a+1)+25

25²=(10.2+5)²=100.2.(2+1)+25=200.3+25=600+25=625

35²=(10.3+5)²=...

85²+75²+65²+55²−45²−35²−25²-15²

=(85²-15²)+(75²-25²)+(65²-35²)+(55²-45²)

=70.100+50.100+30.100+10.100

=160.100=16000

Ban co the giai giup mk dc ko ?

\(\frac{2^{23}\cdot45^{25}\cdot13^{22}\cdot35^{16}}{9^{26}\cdot65^{22}\cdot28^{17}\cdot25^9}=\frac{2^{23}\cdot5^{25}\cdot3^{50}\cdot13^{22}\cdot5^{16}\cdot7^{16}}{3^{52}\cdot5^{22}\cdot13^{22}\cdot7^{17}\cdot2^{54}\cdot5^{18}}=\frac{2^{23}\cdot3^{50}\cdot5^{31}\cdot7^{16}\cdot13^{22}}{2^{54}\cdot3^{52}\cdot5^{22}\cdot7^{17}\cdot13^{22}}=\frac{5^9}{2^{31}\cdot3^2\cdot7}\)
 

Ta có : 25a² + 4b² - 20ab 

= (5a)² - 2.5a.2b + (2b)²

= (5a - 2b)²

Ta có : x² - x + \(\frac{1}{4}\)

= x² - \(2.x.\frac{1}{2}+\frac{1}{2}^2\)

= \(\left(x-\frac{1}{2}\right)^2\)

585

(15+75)+(20+70)+(25+65)+(30+60)+(35+55)+(40+50)+45
= 90+90+90+90+90+90+45
= 90.6+45
= 540+45=585