(1345-13x):7+145=248

(1345-13x):7=248-145

(1345-13x):7=103

1345-13x=103*7

1345-13x=721

13x=1345-721

13x=624

x=624:13

x=48

(1345 - 13x) : 7 + 145 = 248

=> (1345 - 13x) : 7 = 103

=> 1345 - 13x = 721

=> 13x = 624

=> x = 48

vậy_

( 1345 - 13x ) : 7 + 145 = 248

( 1345 - 13x ) : 7 = 248 - 145

( 1345 - 13x ) : 7 = 103

1345 - 13x = 103 . 7 

1345 - 13x = 721

13x = 1345 - 721

13x = 624

x = 624 : 13

x = 48

x=48 nha

hahaha

hihihi 

huhuhu

a: =>13x-144=25

=>13x=169

hay x=13

\(15x-13x+5x=49:7\)

\(\Leftrightarrow7x=7\Leftrightarrow x=1\)

\(15x-13x+5x=49:7\)

\(\Leftrightarrow2x+5x=7\)

\(\Leftrightarrow7x=7\)

\(\Leftrightarrow x=1\)

\(15x-13x+5x=49:7\)

\(\Leftrightarrow7x=7\)

\(\Leftrightarrow x=1\)

a:  =>x-16=74

nên x=90

a, Thay \(x=\frac{7}{13}\)vào \(x+y=40\)=> \(\frac{7}{13}+y=40\Rightarrow y=40-\frac{7}{13}\Rightarrow y=\frac{513}{13}\)

b, Ta có: \(13x=7y\Rightarrow\frac{x}{7}=\frac{y}{13}\)và x+y=-60. Áp dụng tính chất dãy tỉ số bằng nhau ta có:

\(\frac{x}{7}=\frac{y}{13}=\frac{x+y}{7+13}=\frac{-60}{20}=-3\) \(\Rightarrow\hept{\begin{cases}\frac{x}{7}=-3\Rightarrow x=-3\cdot7=-21\\\frac{y}{13}=-3\Rightarrow y=-3\cdot13=-39\end{cases}}\)

1) 6x²+13x+7=0

6x²+6x+7x+7=0

6x(x+1)+7(x+1)=0

(6x+7)(x+1)=0

2)2x²-9x+7=0

2X²-2x-7x+7=0

2x(x-1)+7(x-1)=0

(2x+7)(x-1)=0

x= -7/2