a) A = 3.(x-1)^2 - (x+1)^2 + 2.(x-3)(x+3) - (2x+3)^2 - (5-20x)
= 3.(x^2-2x+1) - (x^2+2x+1) + 2.(x^2-9) - (4x^2+12x+9) - 5 + 20x
= 3x^2 - 6x + 3 - x^2 - 2x -1 + 2x^2 - 18 - 4x^2 - 12x - 9-5 + 20x 
= -30 =< bt k phụ th biến

b) => B= 5x(x^2-7^2)-x(4x^2-4x+1)-x^3-4x^2+246x-175
= 5x^3 - 245x - 4x^3 + 16x^2 -x -x^3 -4x^2 +246x -175
= 12x^2 -175

b, B = 5x(x-7)(x+7) - x(2x-1)^2 - (x^3+4x^2-146x)-175
= 5x^3 - 245x - x(4x^2-4x+1)-x^3 - 4x^2 + 246x - 175
= 4x^3 +x - 4x^2 - 4x^3 + 4x^2 - x -175
= -175