Question

Nhìn tổng quan để nhận ra kiến thức rồi thu gọn

\(A=\left(x-1\right)^2-\left(2x-2\right)\left(2x+3\right)+\left(2x+3\right)^2-x\left(x+8\right)\)

\(B=\left(x+y-1\right)\left(x-y+1\right)+\left(y-1\right)^2\)

Answer 1

\(A=\left(x-1\right)^2-\left(2x-2\right)\left(2x+3\right)+\left(2x+3\right)^2-x\left(x+8\right)\)
\(\Leftrightarrow A=\left(x-1\right)^2-2\left(x-1\right)\left(2x+3\right)+\left(2x+3\right)^2-x\left(x+8\right)\)
\(\Leftrightarrow A=\left(x-1-2x-3\right)^2-x\left(x-8\right)\)
\(\Leftrightarrow A=\left(-x-4\right)^2-x^2-8x\)
\(\Leftrightarrow A=x^2+4x+4-x^2-8x\)
\(\Leftrightarrow A=4-4x\)
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