Question

Tìm x a) (x-3)(x^2+3x+9)+x(4-x^2)=5. b)(x+1)^3-(x-1)^3-6(x-1)^2=-10. Giải cụ thể cho mik vs ạ.nhanh giúp mik vs nhaaa

 

Answer 1

a, (x-3)(x^2+3x+9) + x(4-x^2) = 5.

=> x^3 - 27 + 4x - x^3 = 5

=> 4x - 27 =5

=> 4x = 32   => x= 8

Answer 2

b, ( x+1)^3 - ( x-1 )^3 - 6 (x-1)^2 = -10

=> ( x+1 - x +1 ) [ ( x+1)^2 + (x+1)(x-1) + (x-1)^2 ] - 6(x-1)^2 = -10

=> 2 [ x^2 + 2x +1 + x^2 -1 + x^2 - 2x +1 ] -6(x-1)^2 = -10

=> 2 [ 3x^2 +1] -6( x^2 -2x +1) = -10

=> 6x^2 +2 - 6x^2 +12x -6 =-10

=>12x -4 = -10

=> 12x = -6

=> x= -1/2