Câu hỏi của Thơ Xuân

Question

Rút gọn các biểu thức sau:

a) (x+2)(x-2) - (x-3)(x+1)

b) (2x+1)2 + (3x-1)2 + 2(2x+1)(3x-1)

Lưu Ngọc Hải Đông · Accepted Answer

a)$\left(x+2\right)\left(x-2\right)-\left(x-3\right)\left(x+1\right)$

$\Leftrightarrow x^2-4-x^2-\left(x^2+x-3x-3\right)$

$\Leftrightarrow x^2-4-x^2-x+3x+3$

$\Leftrightarrow2x-1$

b) $\left(2x+1\right)^2+\left(3x-1\right)^2+2\left(2x+1\right)\left(3x-1\right)$

$\Leftrightarrow\left[\left(2x+1\right)+\left(3x-1\right)\right]^2$

$\Leftrightarrow\left(2x+1+3x-1\right)^2=\left(5x\right)^2=25x^2$Câu trả lời: a)$\left(x+2\right)\left(x-2\right)-\left(x-3\right)\left(x+1\right)$

$\Leftrightarrow x^2-4-x^2-\left(x^2+x-3x-3\right)$

$\Leftrightarrow x^2-4-x^2-x+3x+3$

$\Leftrightarrow2x-1$

b) $\left(2x+1\right)^2+\left(3x-1\right)^2+2\left(2x+1\right)\left(3x-1\right)$

$\Leftrightarrow\left[\left(2x+1\right)+\left(3x-1\right)\right]^2$

$\Leftrightarrow\left(2x+1+3x-1\right)^2=\left(5x\right)^2=25x^2$

Cheewin · Answer

a) $\left(x+2\right)\left(x-2\right)-\left(x-3\right)\left(x+1\right)$

$=x^2-4-\left(x^2+x-3x-3\right)$

$=x^2-4-x^2+2x+3$

$=2x-1$

b) $\left(2x+1\right)^2+\left(3x-1\right)^2+2\left(2x+1\right)\left(3x-1\right)$

$=\left(2x+1+3x-1\right)^2$

$=25x^2$Câu trả lời: a) $\left(x+2\right)\left(x-2\right)-\left(x-3\right)\left(x+1\right)$

$=x^2-4-\left(x^2+x-3x-3\right)$

$=x^2-4-x^2+2x+3$

$=2x-1$

b) $\left(2x+1\right)^2+\left(3x-1\right)^2+2\left(2x+1\right)\left(3x-1\right)$

$=\left(2x+1+3x-1\right)^2$

$=25x^2$

Nguyễn Thị Nhân · Answer

a, (x+2) (x-2) - (x - 3) (x+1).

=x2-4 - x2+ 2x +3.

=2x - 1.

b,(2x + 1)2 + (3x-1)2 +2 (2x + 1) ( 3x - 1 ).

=(2x + 1 + 3x -1)2.

= 25 x2Câu trả lời: a, (x+2) (x-2) - (x - 3) (x+1).

=x2-4 - x2+ 2x +3.

=2x - 1.

b,(2x + 1)2 + (3x-1)2 +2 (2x + 1) ( 3x - 1 ).

=(2x + 1 + 3x -1)2.

= 25 x2

Bài 3: Những hằng đẳng thức đáng nhớ