Toán Lớp 8: Tìm x biết (x-1)^2+x.(4-x)=11 (x-5)^2-x.(x+2)=5 x.(x+4)-x^2-6x=10 6x^2-(2x-3).(3x+2)=1

Question

Toán Lớp 8:  Tìm x biết (x-1)^2+x.(4-x)=11                      (x-5)^2-x.(x+2)=5                  x.(x+4)-x^2-6x=10 6x^2-(2x-3).(3x+2)=1                               (x+2).(x-5)+x(1-x)=2                         (x-1).(2-x)+(x-3)^2=4-2x

landinhngoc97 · Answer

Giải đáp:   $a. ( x - 1 )^{2} + x( 4 - x ) = 11$   &hArr; $x^{2} - 2x + 1 + 4x - x^{2} = 11$   &hArr; $2x + 1 = 11$   &hArr; $2x = 10$   &hArr; $x = 5$   $b. ( x - 5 )^{2} - x( x + 2 ) = 5$   &hArr; $x^{2} - 10x + 25 - x^{2} - 2x = 5$   &hArr; $- 12x + 25 = 5$   &hArr; $- 12x = - 20$   &hArr; $x =  frac{5}{3}$   $c. x( x + 4 ) - x^{2} - 6x = 10$   &hArr; $x^{2} + 4x - x^{2} - 6x = 10$   &hArr; $- 2x = 10$   &hArr; $x = - 5$   $d. 6x^{2} - ( 2x - 3 )( 3x + 2 ) = 1$   &hArr; $6x^{2} - 6x^{2} - 4x + 9x + 6 = 1$   &hArr; $5x + 6 = 1$   &hArr; $5x = - 5$   &hArr; $x = - 1$   $e. ( x + 2 )( x - 5 ) + x( 1 - x ) = 2$   &hArr; $x^{2} - 5x + 2x - 10 + x - x^{2} = 2$   &hArr; $- 2x - 10 = 2$   &hArr; $- 2x = 12$   &hArr; $x = - 6$   $f. ( x - 1 )( 2 - x ) + ( x - 3 )^{2} = 4 - 2x$   &hArr; $2x - x^{2} - 2 + x + x^{2} - 6x + 9 = 4 - 2x$   &hArr; $- 3x + 7 = 4 - 2x$   &hArr; $- x = - 3$   &hArr; $x = 3$