b) \(B=\)ghi lại đề nha bn
Đặt \(x^2+4x-3=t\) ta có:
\(B=t^2-5xt+6x^2\)
\(B=t^2-2xt-3xt+6x^2\)
\(B=t\left(t-2x\right)-3x\left(t-2x\right)=\left(t-2x\right)\left(t-3x\right)\)
\(B=\left(x^2+4x-3-2x\right)\left(x^2+4x-3-3x\right)\)
\(B=\left(x^2+2x-3\right)\left(x^2+x-3\right)\)
bn làm tương tự câu c) cũng như vậy nha!!!
\(A=\left(x^2-2x\right)\left(x^2-2x-1\right)-6\)
\(=\left(x^2-2x\right)^2-\left(x^2-2x\right)-6\)
\(=\left(x^2-2x\right)^2-\left(x^2-2x\right)+\frac{1}{4}-\frac{25}{4}\)
\(=\left(x^2-2x+\frac{1}{2}\right)^2-\frac{25}{4}\)
\(=\left(x^2-2x+\frac{1}{2}-\frac{5}{2}\right)\left(x^2-2x+\frac{1}{2}+\frac{5}{2}\right)\)
\(=\left(x^2-2x-2\right)\left(x^2-2x+3\right)\)