Tính nhanh (4x^2 – 9y^2) : (2x – 3y)

Luyện tập (trang 32)

Bài 73 trang 32 Toán 8 Tập 1: Tính nhanh

a) (4x² – 9y²) : (2x – 3y)

b) (27x³ – 1) : (3x – 1)

c) (8x³ + 1) : (4x² – 2x + 1)

d) (x² – 3x + xy – 3y) : (x + y)

Trả lời

a) (4x² – 9y²) : (2x – 3y) = (2x + 3y) (2x – 3y) : (2x – 3y) = 2x + 3y

b) (27x³ – 1) : (3x – 1)= (3x – 1) (9x²+3x+1): (3x – 1) = (9x²+3x+1)

c) (8x³ + 1) : (4x² – 2x + 1) = (2x + 1) (4x² – 2x + 1) : (4x² – 2x + 1)

= 2x + 1

d) (x² – 3x + xy – 3y) : (x + y) = : (x + y)

= (x – 3) (x + y) : (x + y) = x – 3