x = 2 nhé

71+ 65x4 = (x+140) :x + 260

71 + 260 = x:x + 140:x + 260

71 + 260 - 1- 260 = 140x

70 = 140x 

x= 70 : 140

x= 1/2

71 + 65 x 4 = x + 140/x + 260

x + 140/x + 260 = 71 + 65 x 4

x + 140/x + 260 = 71 + 260

x + 140/x = 71

x/x + 140/x  = 71

1 + 140/x = 71

140/x = 71 - 1

140/x = 70

     x = 140/70

     x = 2

   ích=2

nhớ nha !

71+ 65 x 4 = (X+14) /X + 260

71 + 260 = X : X + 14 : X + 260

71 = 1 + 14 : X (Cùng bớt 2 vế đi 260)

1 + 14 : X = 71 (đảo vế)

14 : X = 71 - 1

14 : X = 70

X = 14 : 70

X = 0,2

mik nha !!!

71 + 65 x 4 = \(\frac{x+140}{x+260}\)

71 + 260 = \(\frac{x+140}{x+260}\)

331 = \(\frac{x+140}{x+260}\)

\(\Rightarrow x+140=331\left(x+260\right)\)

\(\Rightarrow x+140=331x+86060\)

\(\Rightarrow140-86060=331x-x\)

\(\Rightarrow330x=85920\)

\(\Rightarrow x=\frac{2864}{11}\)

(x+1)+(x+4)+(x+7)+....+(x+28)=155

x+x+x+...+x+(1+4+7+....+28) = 155

10x + 145 = 155

=> 10x = 155 - 145

=> 10x = 10

=> x = 10:10

=> x =1

a) (x + 1 ) + ( x + 4 ) + ( x + 7 ) + ... +  ( x + 28 ) = 155

( x + x + x + ... + x ) + ( 1 + 4 + 7 + ... + 28 ) = 155

10x + 145 = 145

10x = 155 - 145

10x = 10

=> x = 10 : 10

=> x = 1

tôi chỉ trả lời cho phần e thôi . Vi phan d của bạn tôi làm dài lam

\(71+65\times4=\frac{x+140}{x}+260\)

                   \(71+260=\frac{x}{x}+\frac{140}{x}+260\)

                   \(71\)              \(=1+\frac{140}{x}\)

                   \(70\)              \(=\frac{140}{x}\)

                   \(x\)                \(=2\) 

\(\frac{x+140}{x+260}=71+65.4\)

\(\Leftrightarrow\frac{x+140}{x+260}=71+260\)

\(\Leftrightarrow\frac{x+140}{x+260}=331\)

\(\Leftrightarrow x+140=\left(x+260\right)331\)

\(\Leftrightarrow x+140=86060+331x\)

\(\Leftrightarrow x-331x=85920\)

\(\Leftrightarrow x\left(331-1\right)=85920\)

\(\Leftrightarrow x330=85920\)

\(\Leftrightarrow x\approx260,2\)