a, (10x3y - 5x2y2 - 25x4y3) : (-5xy)
= -2x2 + xy + 5x3y2
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b, [15(x - y)5 - 9(x - y)4 + 12(y - x)2 ] : (y - x)2
= [15(x - y)5 - 9(x - y)4 + 12(x - y)2 ] : (x - y)2
= 15(x - y)3 - 9(x - y)2 + 12
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c, (27x3 - y3) : (3x - y)
= (3x - y)(9x2 + 3xy + y2) : (3x - y)
= 9x2 + 3xy + y2
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d, (15x4 + 4x3 + 11x2 + 14x - 8) : (5x2 + 3x - 2)
= (15x4 + 9x3 - 5x3 - 6x2 - 3x2 + 20x2 + 2x + 12x - 8)
= [(15x4 + 9x3 - 6x2) - (5x3 + 3x2 - 2x) + (20x2 + 12x - 8)] : (5x2 + 3x - 2)
= [3x2(5x2 + 3x - 2) - x(5x3 + 3x - 2) + 4(5x2 + 3x - 2)] : (5x2 + 3x - 2)
= (5x2 + 3x - 2)(3x2 - x + 4) : (5x2 + 3x - 2)
= 3x2 - x +4