Toán Lớp 7: Tìm x , biết : ( 2x+3) ³ =1/8 (3x-1) ²=16/25 (x-2)^2019=(x-2)^2021

Question

Toán Lớp 7:  Tìm x , biết :  ( 2x+3)  ³ =1/8 (3x-1)  ²=16/25 (x-2)^2019=(x-2)^2021

lantrungbach · Answer

(2x+3)^3 =1/8   -> (2x+3)^3 = (1/2)^3   -> 2x + 3 = 1/2   -> 2x = 1/2 - 3   -> 2x = 3/6 - 18/6   -> 2x = -15/6   -> x = -15/12 = -5/4   Vậy x = -5/4   $  $   (3x -1)^2 = 16/25   -> (3x-1)^2 = (4/5)^2   -> 3x - 1 = 4/5 hoặc 3x -1 = -4/5     X&eacute;t 3x -1 =4/5   -> 3x = 9/5   -> x = 9/15   -> x = 3/5   X&eacute;t 3x - 1 = -4/5   -> 3x = -4/5 +1   -> 3x = 1/5   -> x = 1/15   Vậy x  in { 3/5 ; 1/15 }   $  $   (x-2)^2019 = (x-2)^2021   -> (x-2)^2021 - (x-2)^2019 = 0   -> (x-2)^2019[ (x-2)^2 - 1 ] = 0   -> (x-2)^2019 = 0 hoặc (x-2)^2 -1 = 0   X&eacute;t (x-2)^2019 =0   -> x - 2 =0   -> x = 2   X&eacute;t (x-2)^2 - 1= 0   -> (x-2)^2 = 1   -> (x-2)^2 = 1^2   -> x - 2 = 1 hoặc x -2 =-1   -> x =3 hoặc x = 1   Vậy x  in { 2 ; 3 ; 1}

phuongthaongoc · Answer

( 2x+3)^3 =1/8       => ( 2x+3)^3 =(1/2)^3       => 2x+3 = 1/2       => 2x = -5/2       => x = -5/4       (3x-1)^2 = 16/25       => (3x-1)^2 = (4/5)^2       =>  ( left[  begin{array}{l}3x-1= frac{4}{5}  3x-1=- frac{4}{5} end{array}  right. )        =>  ( left[  begin{array}{l}3x= frac{9}{5}  3x= frac{1}{5} end{array}  right. )        =>  ( left[  begin{array}{l}x= frac{9}{15}  x= frac{1}{15} end{array}  right. )        (x-2)^2019=(x-2)^2021       => (x-2)^2021 - (x-2)^2019 = 0       => (x-2)^2019 . ((x-2)^2 - 1) = 0       X&eacute;t (x-2)^2019 = 0       => x-2 = 0       => x = 2       X&eacute;t (x-2)^2 - 1 = 0       => (x-2)^2 = 1       Th1: x - 2 = 1       => x = 3       Th2: x - 2 = -1       => x = 1       (Ch&uacute;c bạn học tốt)