Phân tích đa thức thành nhân tử
x2-11x+2
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\(x^2-11x+3\\ =\left(x^2-4x+4\right)-7x-1\\ =\left(x-2\right)^2-\left(\sqrt{7x+1}\right)^2\\ =\left(x-2-\sqrt{7x+1}\right)\left(x-2+\sqrt{7x+1}\right)\)
\(x^2-4-3\left(x-2\right)=\left(x-2\right)\left(x-1\right)\)
\(=x^2+x-6x+6\\ =x\left(x+1\right)-6\left(x+1\right)\\ =\left(x+1\right)\left(x+6\right)\)
\(x^2-3x-4=x^2+x-4x-4=x\left(x+1\right)-4\left(x+1\right)=\left(x-4\right)\left(x+1\right)\)
\(x^2-6x+7=x^2-6x+9-2\\ =\left(x-3\right)^2-2=\left(x-3-\sqrt{2}\right)\left(x-3+\sqrt{2}\right)\\ x^4+64=x^4+16x^2+64-16x^2\\ =\left(x^2+8\right)^2-16x^2=\left(x^2-4x+8\right)\left(x^2+4x+8\right)\\ a^4+4b^4=a^4+4a^2b^2+4b^4-4a^2b^2\\ =\left(a^2+2b^2\right)^2-4a^2b^2\\ =\left(a^2-2ab+2b^2\right)\left(a^2+2ab+2b^2\right)\)
= x2 -7x -x +7
= x. (x-7) - (x-7)
= (x-1)(x-7)
Chúc bạn học tốt nha!
\(x^2-2xy+y^2+3x-3y-4\)
\(=\left(x-y\right)^2-1+3x-3y-3\)
\(=\left[\left(x-y\right)^2-1^2\right]+\left(3x-3y-3\right)\)
\(=\left[\left(x-y\right)-1\right]\left[\left(x-y\right)+1\right]+3\left(x-y-1\right)\)
\(=\left(x-y-1\right)\left(x-y+1\right)+3\left(x-y-1\right)\)
\(=\left(x-y-1\right)\left[\left(x-y+1\right)+3\right]\)
\(=\left(x-y-1\right)\left(x-y+4\right)\)
\(x^2+4xy+4y^2-25\)
\(=\left(x^2+4xy+4y^2\right)-25\)
\(=\left(x+2y\right)^2-5^2\)
\(=\left(x+2y+5\right)\left(x+2y-5\right)\)
\(x^2-11x+2\)
\(\text{Sử dụng biệt thức( cách này lớp 9 kì 2 hok nha)}\)
\(\text{denta}=b^2-4ac=11^2-2.1.4=113>0\)
=> pt có 2 No là:
\(x_1=\frac{11+\sqrt{113}}{2};x_2=\frac{11-\sqrt{113}}{2}\)
\(x^2-11x+2\)
\(=\left[x^2-2.x.\frac{11}{2}+\left(\frac{11}{2}\right)^2\right]-\frac{7}{2}\)
\(=\left(x-\frac{11}{2}\right)^2-\left(\sqrt{\frac{7}{2}}\right)^2\)
\(=\left(x-\frac{11}{2}+\sqrt{\frac{7}{2}}\right)\left(x-\frac{11}{2}-\sqrt{\frac{7}{2}}\right)\)
\(=\left(x-\frac{11}{2}+\frac{\sqrt{14}}{2}\right)\left(x-\frac{11}{2}-\frac{\sqrt{14}}{2}\right)\)
\(=\left(x+\frac{\sqrt{14}-11}{2}\right)\left(x-\frac{\sqrt{14}+11}{2}\right)\)
Tham khảo nhé~