K = (x-4)^2 - (2x-1)^2
= (x-4-(2x-1)) * (x-4+2x-1)
= (x-4-2x+1) * (3x - 5)
= (-x-3) * (3x - 5)
L = (7x+8)^2 - (9-5x)^2
= (7x+8-(9-5x)) * (7x+8+9-5x)
= (7x+8-9+5x) * (2x+17)
= (12x-1) * (2x+17)
A = (x+7)(3-2x) + (5x-2)(4x+1)
= 3x - 2[tex]x^{2}[/tex] +21 - 14x + 20[tex]x^{2}[/tex] + 5x - 8x -2
= 18[tex]x^{2}[/tex] - 14x + 19
B = (5x-2)(5x-8) - (3x-5)(x+7)
= 25[tex]x^{2}[/tex] - 40x - 10x + 16 - (3[tex]x^{2}[/tex] +21x -5x - 35)
= 25[tex]x^{2}[/tex] - 40x - 10x + 16 - 3[tex]x^{2}[/tex] - 21 + 5x + 35
= 22[tex]x^{2}[/tex] - 6x + 51
C = (2x+3)(5x-8)-(2x-4)(5x-1)
= 10[tex]x^{2}[/tex] - 16x + 15x - 24 - (10[tex]x^{2}[/tex] - 2x - 20x + 4)
= 10[tex]x^{2}[/tex] -16x + 15x -24 - 10[tex]x^{2}[/tex] + 2x + 20x -4
= 21x - 28
