tìm x trong tỉ lệ thức sau a. x – 1 / x + 5 = 7/9 b.x^2/ 6 = 24/25 c. x-2/x-1=x+4/x+7 d. x-3/x+5=5/7 g. x-1/x+2=x-2/x+3 giúp mik vs ạ đg cânf gấp c

0 bình luận về “tìm x trong tỉ lệ thức sau a. x – 1 / x + 5 = 7/9 b.x^2/ 6 = 24/25 c. x-2/x-1=x+4/x+7 d. x-3/x+5=5/7 g. x-1/x+2=x-2/x+3 giúp mik vs ạ đg cânf gấp c”

1. Đáp án:

    

   Giải thích các bước giải:

   a) ( x – 1 )/( x + 5 ) = 7/9

   <-> ( x – 1 ) . 9 = ( x + 5 ) . 7

   <-> 9x – 9 = 7x + 35

   <-> 9x-7x=9+35

   <->2x=44

   <-> x = 22

   b) x^2/6 = 24/25

   <-> x^2 . 25 = 6 . 24

   <-> x^2 . 25 = 144

   <-> x^2 .5^2=12^2 =(-12)^2

   <-> x = 12/5 và x=-12/5

   c) ( x – 2 )/( x – 1 ) = ( x + 4 )/( x + 7 )

   <-> ( x – 2 )( x + 7 ) = ( x – 1 )( x + 4 )

   <-> x^2 + 7x – 2x – 14 = x^2 + 4x – x – 4

   <-> 5x – 14 = 3x – 4

   <-> 2x = 10

   <-> x = 5

   d) ( x – 3 )/( x + 5 ) = 5/7

   <-> ( x – 3 ) . 7 = ( x + 5 ) . 5

   <-> 7x – 21 = 5x + 25

   <-> 2x = 46

   <-> x = 23

   g) ( x – 1 )/( x + 2 ) = ( x – 2 )/( x + 3 )

   <-> ( x – 1 )( x + 3 ) = ( x + 2 )( x – 2 )

   <-> x^2 – x + 3x – 3 = x^2 – 2^2

   <-> 2x – 3 = – 4

   <-> 2x = -1

   <-> x = -1/2

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2. Bài làm

   a) ( x – 1 )/( x + 5 ) = 7/9

   <=> ( x – 1 ) . 9 = ( x + 5 ) . 7

   <=> 9x – 9 = 7x + 35

   <=> 2x = 44

   <=> x = 22

   Vậy x = 22.

   b) x^2/6 = 24/25

   <=> x^2 . 25 = 6 . 24

   <=> x^2 . 25 = 144

   <=> x^2 = 5,76

   <=> x = ±2,4

   Vậy x =± 2,4.

   c) ( x – 2 )/( x – 1 ) = ( x + 4 )/( x + 7 )

   <=> ( x – 2 )( x + 7 ) = ( x – 1 )( x + 4 )

   <=> x^2 + 7x – 2x – 14 = x^2 + 4x – x – 4

   <=> 5x – 14 = 3x – 4

   <=> 2x = 10

   <=> x = 5

   Vậy x = 5.

   d) ( x – 3 )/( x + 5 ) = 5/7

   <=> ( x – 3 ) . 7 = ( x + 5 ) . 5

   <=> 7x – 21 = 5x + 25

   <=> 2x = 46

   <=> x = 23

   Vậy x = 23.

   g) ( x – 1 )/( x + 2 ) = ( x – 2 )/( x + 3 )

   <=> ( x – 1 )( x + 3 ) = ( x + 2 )( x – 2 )

   <=> x^2 – x + 3x – 3 = x^2 – 4

   <=> 2x – 3 = – 4

   <=> 2x = -1

   <=> x = -1/2

   Vậy x = -1/2

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