Toán Lớp 8: 1)Tìm x a) (2x-3) (3-4x)=0 b) (2x-5)^2=9 2) Rút gọn tính gt A tại x=0,001 A= (x+1)(x^2-x+1)-(x-1)(x^2+x+1)+x

Question

Toán Lớp 8:  1)Tìm x a) (2x-3) (3-4x)=0 b) (2x-5)^2=9 2) Rút gọn tính gt A tại x=0,001 A= (x+1)(x^2-x+1)-(x-1)(x^2+x+1)+x

thaolanphuobg · Answer

Gửi bạn!

maianhtuanh · Answer

C&acirc;u 1 :   a) ( 2x - 3 )( 3 - 4x ) = 0   =>  ( left[  begin{array}{l}2x-3=0  3-4x=0 end{array}  right. )    =>  ( left[  begin{array}{l}2x=3  4x=3 end{array}  right. )    =>  ( left[  begin{array}{l}x=3/2  x=3/4 end{array}  right. )    b)   ( 2x-5 )&sup2;=  9           ( 2x-5 )&sup2; = &plusmn;3&sup2;     => 2x - 5 = &plusmn; 3     =>  ( left[  begin{array}{l}2x-5=3  2x-5=-3 end{array}  right. )      =>  ( left[  begin{array}{l}2x=8  2x=2 end{array}  right. )      =>  ( left[  begin{array}{l}x=4  x=1 end{array}  right. )      C&acirc;u 2 :     A= ( x+1 )( x&sup2;- x + 1 ) - ( x - 1 )(x&sup2; + x + 1 ) + x     A = x&sup3; - x&sup2; + x + x&sup2; - x + 1 - x&sup3; + x&sup2; + x - x&sup2; - x - 1 + x     A = x      Tại x = 0,001     => A = 0,001     Vậy A = 0,001 tại x = 0,001