Thu gọn biểu thức:a) 5x3y : xy – 2x2+ 10;b) 2x(3x + 2) + (4x + 3)(2x – 1);c) (x + 2)2– (x + 5)(x – 5);d) (4x + 5)2– (8x + 10)(1 – 3x) + (1 – 3x)2.

* Hướng dẫn giải

Hướng dẫn giải

a) 5x³y : xy – 2x²+ 10

= 5x²– 2x²+ 10

= 3x²+ 10

b) 2x(3x + 2) + (4x + 3)(2x – 1)

= 6x²+ 4x + 8x²– 4x + 6x – 3

= 14x²+ 6x – 3

c) (x + 2)²– (x + 5)(x – 5)

= x²+ 4x + 4 – x²+ 25

= 4x + 29

d) (4x + 5)²– (8x + 10)(1 – 3x) + (1 – 3x)²

= (4x + 5)² – 2(4x + 5)(1 – 3x) + (1 – 3x)²

⁼ [(4x + 5) – (1 – 3x)]²

= (4x + 5 – 1+ 3x)²

= (7x + 4)²

= 49x²+ 56x + 16