Áp dụng t/c dãy tỉ số bằng nhau, ta có:

\(\frac{2x+2}{5x-3}=\frac{2x+12}{5x+18}=\frac{\left(2x+12\right)-\left(2x+2\right)}{\left(5x+18\right)-\left(5x-3\right)}=\frac{10}{21}\)

Có: \(\frac{2x+2}{5x-3}=\frac{10}{21}\)

<=> 21(2x+2) = 10(5x-3)

<=> 42x+42 = 50x-30

<=> 8x = 72

<=> x = 9

\(\frac{2x+2}{5x-3}=\frac{2x+12}{5x+18}\)

=> ( 2x + 2 ) ( 5x + 18 ) = ( 2x + 12 ) ( 5x - 3 )

=> 2x ( 5x + 18 ) + 2 ( 5x + 18 ) = 2x ( 5x - 3 ) + 12 ( 5x - 3 )

=> 10 x ² + 36x + 10x + 36       = 10 x ² - 6x + 60 x - 36

=>  36x + 10x + 6x - 60x           = - 36 - 36

=>  - 8 x                                    = - 72

=>       x                                    = 9

\(\frac{2x+2}{5x-3}=\frac{2x+12}{5x+18}\)

\(\Rightarrow\left(2x+2\right)\left(5x+18\right)=\left(5x-3\right)\left(2x+12\right)\)

\(\Rightarrow2x\left(5x+18\right)+2\left(5x+18\right)=5x\left(2x+12\right)-3\left(2x+12\right)\)

\(\Rightarrow10x^2+36x+10x+36=10x^2+60x-6x-36\)

\(\Rightarrow46x+36=54x-36\)

\(\Rightarrow36+36=54x-46x\)

\(\Rightarrow72=8x\)

\(\Rightarrow x=9\)

tck cho to nha 

2x(5x+18)+2(5x+18)=5x(2x+12)+3(3x-1)

10x^2+2x+10x+2=10x+-5x+9x-3

=> 10x^2+2x+10x-10x^2+5x-9x=-3-2

-2X=-5

x=5/2

x=5/2

a) 2|2/3 - x| = 1/2

|2/3 - x| = 1/4

|2/3 - x| = 1/4 hoặc |2/3 - x| = -1/4

Xét 2 TH...

=> ( 2x+2).(5+18)= (2x+12). (5x-3)

=> (2x+2) . 23  =  2x. 5x - 2x.3 + 12.5x - 12.3

=> 2x. 23+ 2.23 =  10.x.x - 6x+ 60x - 36

=> 46x + 46  =  10x.x + 54 x -36

=> 46 + 36  =  10xx + 54x -46x

=>  82 = 10xx +8x

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