$\text{A = (5x - 7)(2x + 3) - (7x + 2)(x - 4) tại x = $\dfrac{1}{2}$}$

`A = 10x^2 + 15x - 14x - 21 - 7x^2 + 28x - 2x + 8`

`A = 3x^2 + 27x - 13`

$\text{Thay x = $\dfrac{1}{2}$}$

`⇒ A = 3 . (1/2)^2 + 27 . 1/2 - 13`

`⇒ A = 3/4 + 27/2 - 13`

`⇒ A = 5/4`

$\text{B = (x - 9)(2x + 3) - 2(x + 7)(x - 5) tại x = $\dfrac{-1}{2}$}$

`B = 2x^2 + 3x - 18x - 27 - 2(x^2 - 5x + 7x - 35)`

`B = 2x^2 -15x - 27 - 2x^2 + 10x - 14x + 70`

`B = -19x + 43`

$\text{Thay x = $\dfrac{-1}{2}$}$

`⇒ B = -19 . $\dfrac{-1}{2}$ + 43`

`⇒ B = 19/2 + 43`

`⇒ B = 105/2`

$\text{C = (-5x + 4)(3x - 2) + (-2x + 3)(x - 2) tại x = -2}$

`C = -15x^2 + 10x + 12x - 8 - 2x^2 + 4x + 3x - 6`

`C = -17x^2 + 29x - 14`

$\text{Thay x = -2}$

`⇒ C = -17 . (-2)^2 + 29 . (-2) - 14`

`⇒ C = -68 - 58 - 14`

`⇒ C = -140`

$\text{D = (x - 5)(-3x + 1) - 3(x - 2)(2x - 1) tại x = $\dfrac{1}{3}$}$

`D = -3x^2 + x + 15x - 5 - 3(2x^2 - x - 4x + 2)`

`D = -3x^2 + 16x - 5 - 6x^2 + 3x + 12x - 6`

`D = -9x^2 + 31x - 11`

$\text{Thay x = $\dfrac{1}{3}$}$

`⇒ D = -9 . (1/3)^2 + 31 . 1/3 - 11`

`⇒ D = -1 + 31/3 - 11`

`⇒ D = -5/3`

$\text{E = (x - 7)(x + 8) - (x - 5)(x - 2) tại x = $\dfrac{1}{5}$}$

`E = x^2 + 8x - 7x - 56 - x^2 + 2x + 5x - 10`

`E = 8x - 66`

$\text{Thay x = $\dfrac{1}{5}$}$

`⇒ E = 8 . 1/5 - 66`

`⇒ E = 8/5 - 66`

`⇒ E = -322/5`

$\text{F = -3(x - 8)(2x + 1) - (x + 5)(-3x + 2) - 4x(x - 6) tại x = -3}$

`F = -3(2x^2 + x - 16x - 8) + 3x^2 - 2x + 15x - 10 - 4x^2 + 24x`

`F = -6x^2 - 3x + 48x + 24 - x^2 + 37x - 10`

`F = -7x^2 + 82x + 14`

$\text{Thay x = -3}$

`⇒ F = -7 . (-3)^2 + 82 . (-3) + 14`

`⇒ F = -63 - 246 + 14`

`⇒ F = -295`

$\text{G = (5x - 4)(-2x + 5) - 7x(x^2 - 4x + 3) + (x^2 - 4x)(7x - 2) tại x = 1}$

`G = -10x^2 + 25x + 8x - 20 - 7x^3 + 28x^2 - 21x + 7x^3 - 2x^2 - 28x^2 + 8x`

`G = -12x^2 + 20x - 20`

$\text{Thay x = 1}$

`⇒ G = -12 . 1^2 + 20 . 1 - 20`

`⇒ G = -12 + 20 - 20`

`⇒ G = -12`

$\text{H = (-3x + 5)(x - 6) - (x - 1)(x^2 - 2x + 3) + (x + 2)(x^2 - 3) tại x = -1}$

`H = -3x^2 + 18x + 5x - 30 - x^3 + 2x^2 - 3x + x^2 - 2x + 3 + x^3 - 3x + 2x^2 - 6`

`H = 2x^2 + 15x - 33`

$\text{Thay x = -1}$

`⇒ H = 2. (-1)^2 + 15 . (-1) - 33`

`⇒ H = 2 - 15 - 33`

`⇒ H = -46`