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\(x^2+7x+12=x\left(x+3\right)+4\left(x+3\right)=\left(x+3\right)\left(x+4\right)\)
\(=x^2+3x+4x+12\)
\(=x\left(x+3\right)+4\left(x+3\right)\)
\(=\left(x+3\right)\left(x+4\right)\)
\(=x^2+2x\cdot\frac{1}{2}+\frac{1}{4}-\left(\frac{\sqrt{23}}{2}i\right)^2\)
\(=\left(x+\frac{1}{2}\right)^2\)\(-\left(\frac{\sqrt{23}}{2}i\right)^2\)
\(\left(x+\frac{1}{2}-\frac{\sqrt{23}}{2}i\right)\left(x+\frac{1}{2}+\frac{\sqrt[]{23}}{2}i\right)\)
\(\dfrac{1}{4}x^2+2xy+4y^2=\left(\dfrac{1}{2}x+2y\right)^2\)
\(=\left(x+y\right)\left(x^2-xy+y^2\right)+2x\left(x+y\right)\)
\(=\left(x+y\right)\left(x^2-xy+y^2+2x\right)\)
\(x^2+5x-2=\left(x^2+2.x.\frac{5}{2}+\frac{25}{4}\right)-\frac{25}{4}-2=\left(x+\frac{5}{2}\right)^2-\frac{33}{4}\)
\(=\left(x+\frac{5}{2}\right)^2-\left(\frac{\sqrt{33}}{2}\right)^2=\left(x+\frac{5}{2}-\frac{\sqrt{33}}{2}\right)\left(x+\frac{5}{2}+\frac{\sqrt{33}}{2}\right)\)
\(=\left(x+\frac{5-\sqrt{33}}{2}\right)\left(x+\frac{5+\sqrt{33}}{2}\right)\)
\(x^4+2002x^2-2001x+2002\)
\(=x^4+2002x^2+x-2002x+2002\)
\(=\left(x^4+x\right)+\left(2002x^2-2002x+2002\right)\)
\(=x\left(x^3+1\right)+2002\left(x^2-x+1\right)\)
\(=x\left(x+1\right)\left(x^2-x+1\right)+2002\left(x^2-x+1\right)\)
\(=\left(x^2-x+1\right)\left[x\left(x+1\right)+2002\right]\)
\(=\left(x^2-x+1\right)\left(x^2+x+2002\right)\)
\(x^4-5x^2y^2+4y^4\)
\(=\left(x^2\right)^2-2x^22y^2+\left(2y^2\right)^2-x^2y^2\)
\(=\left(x^2-2y^2\right)^2-\left(xy\right)^2\)
\(=\left(x^2-2y^2-xy\right)\left(x^2-2y^2+xy\right)\)
ko ra được đâu
Ta có: \(\Delta\)= b^2 - 4ac
= (-6)^2 - 4.1.15
=-24
Vì\(\Delta\)< 0 nên phương trình vô nghiệm => không thể phân tích