Question

Rút gọn biểu thức:

a) (x + 2)(x – 2) – (x + 1)2

b) (2x – 1)(4x2 + 2x + 1) – (2x + 1)( 4x2 – 2x + 1)

3. Tìm x biết:

a) (x + 2)(x2 – 2x + 4) – x(x2 – 2) = 15

b) (x – 1)3 – x(x2 – 3x – 4) = 13

thanks

Answer 1

\(a,=x^2-4-x^2-2x-1=-2x-5\\ b,=8x^3-1-8x^3-1=-2\\ 3,\\ a,\Rightarrow x^3+8-x^3+2x=15\\ \Rightarrow2x=7\Rightarrow x=\dfrac{7}{2}\\ b,\Rightarrow x^3-3x^2+3x-1-x^3+3x^2+4x=13\\ \Rightarrow7x=14\Rightarrow x=2\)

Answer 2

Bài 2:

a) \(=x^2-4-x^2-2x-1=-2x-5\)

b) \(=8x^3-1-8x^3-1=-2\)

Bài 3:

a) \(\Rightarrow x^3+8-x^3+2x=15\)

\(\Rightarrow2x=7\Rightarrow x=\dfrac{7}{2}\)

b) \(\Rightarrow x^3-3x^2+3x-1-x^3+3x^2+4x=13\)

\(\Rightarrow7x=14\Rightarrow x=2\)