Câu hỏi của Linh

Question

rút gọn biểu thức

$\left(a+b-c\right)^2+\left(a-b+c\right)^2-2\left(b-c\right)^2$

Fairy Tail · Accepted Answer

$A=\left(a+b-c\right)^2+\left(a-b+c\right)^2-2\left(b-c\right)^2$

$A=\left(a+b-c\right)^2+\left(a-b+c\right)^2-\left(b-c\right)^2-\left(b-c\right)^2$

$A=\left[\left(a+b-c\right)^2-\left(b-c\right)^2\right]+\left[\left(a-b+c\right)^2-\left(b-c^2\right)\right]$

$A=\left[\left(a+b-c-b+c\right)\left(a+b-c+b-c\right)\right]+\left[\left(a-b+c-b+c\right)\left(a-b+c+b-c\right)\right]$

$A=\left[a\left(a+2b\right)\right]+\left[a\left(a-2b+2c\right)\right]$

$A=a\left(a+2b+a-2b+2c\right)$

$A=a\left(2a+2c\right)$Câu trả lời: $A=\left(a+b-c\right)^2+\left(a-b+c\right)^2-2\left(b-c\right)^2$

$A=\left(a+b-c\right)^2+\left(a-b+c\right)^2-\left(b-c\right)^2-\left(b-c\right)^2$

$A=\left[\left(a+b-c\right)^2-\left(b-c\right)^2\right]+\left[\left(a-b+c\right)^2-\left(b-c^2\right)\right]$

$A=\left[\left(a+b-c-b+c\right)\left(a+b-c+b-c\right)\right]+\left[\left(a-b+c-b+c\right)\left(a-b+c+b-c\right)\right]$

$A=\left[a\left(a+2b\right)\right]+\left[a\left(a-2b+2c\right)\right]$

$A=a\left(a+2b+a-2b+2c\right)$

$A=a\left(2a+2c\right)$

Bài 1: Nhân đơn thức với đa thức