... = x(x4 -5 x2 + 4) (0,25) = x[x2( x2 -1 )-4 (x2 -1 )] (0,5) = x( x2 -1 )(x2 -4 ) (0,25) = (x-2)(x-1)x(x+1)(x+2) (0,5)b/ (1đ) A = a2(2a - 3) + b2 (-3 + 2b) = 2(a3+b3 )-3 (a2+b2) ... 2a2c2) - c4(0,5) = (2ab)2 - [(a2+b2)2 -2 c2(a2+b2)+c4] = (2ab)2 -[ (a2+b2) - c2]2(0,25) = (2ab + a2 + b2 - c2)(2ab - a2 - b2+c2) = (a+b+c)(a+b-c)(c+a-b)(c-a+b) ... (2,5đ)a) (1,25đ) x3 - 3x + a = (x2 - 2x +1)(x +2) + a - 2(0,75)(x3 - 3x + a) chia hết cho (x - 1)2 ⇔a-2 = 0 ⇔a = 2 (0,5)b) (1,25đ) x2 (x -1 ) + 2x (1-x) = 0 ⇔x(x-1)(x-2) = 0 (0,5)Vậy...