Giải câu 73 bài: Luyện tập sgk Toán 8 tập 1 Trang 32.
a) (4x2 – 9y2) : (2x – 3y) = [(2x)2 – (3y)2] : (2x – 3y)
= 2x + 3y;
b) (27x3 – 1) : (3x – 1) = [(3x)3 – 1] : (3x – 1)
= (3x)2 + 3x + 1
= 9x2 + 3x + 1
c) (8x3 + 1) : (4x2 – 2x + 1) = [(2x)3 + 1] : (4x2 – 2x + 1)
= (2x + 1)[(2x)2 – 2x + 1] : (4x2 – 2x + 1)
= (2x + 1)(4x2 – 2x + 1) : (4x2 – 2x + 1) = 2x + 1
d) (x2 – 3x + xy -3y) : (x + y)
= [(x2 + xy) – (3x + 3y)] : (x + y)
= [x(x + y) – 3(x + y)] : (x + y)
= (x + y)(x – 3) : (x + y)
= x – 3.