`81/625 = (3/5)^x` `(1/3 – 3/2 x )^2 = 9/4`

2 bình luận về “`81/625 = (3/5)^x` `(1/3 – 3/2 x )^2 = 9/4`”

1. 81/625 = ( 3/5 )^x

   ⇒ ( 3/5 )^4 = ( 3/5 )^x

   ⇒ x = 4

   Vậy x = 4

   ______

   ( 1/3 – 3/2x )^2 = 9/4

   ⇒ ( 1/3 – 3/2 x )^2 = ( 3/2 )^2 = ( -3/2 )^2

   TH1:

   1/3 – 3/2 x = 3/2

   ⇒ 3/2 x = 1/3 – 3/2

   ⇒ 3/2 x = 2/6 – 9/6

   ⇒ 3/2 x = -7/6

   ⇒ x = -14/27

   TH2:

   1/3 – 3/2 x =  -3/2

   ⇒ 3/2 x = 1/3 – – 3/2

   ⇒ 3/2 x = 2/6 + 9/6

   ⇒ 3/2 x = 11/6

   ⇒ x = 11/9

   Vậy x ∈ { -14/27 ; 11/9 }

   Trả lời
2. Giải đáp:

   81/625 = (3/5)^x

   (3/5)^4 = (3/5)^x

   => x = 4

   Vậy x=4

   (1/3 – 3/2 x)^2 = 9/4

   (1/3 – 3/2 x)^2 = (3/2)^2 = (-3/2)^2

   TH1: 1/3 – 3/2 x = 3/2

           3/2 x = 1/3 – 3/2

           3/2 x = -7/6

             x = -7/6 : 3/2

             x= -7/9

   TH2: 1/3 – 3/2 x = -3/2

            3/2 x = 1/3 – (-3/2)

            3/2 x = 11/6

             x = 11/6 : 3/2

             x = 11/9

   Vậy x in {11/9;-7/9}

    

    

   Trả lời