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= (x^4 + 2x^3 + x^2) + x + 1
= (x^2 + x)^2 + (x + 1)
= [x. (x + 1)]^2 + (x + 1)
= x^2 . (x + 1)^2 + (x + 1)
= (x + 1).[x^2. (x + 1) + 1]
= (x + 1). (x^3 + x^2 + 1)
Không hiểu hỏi lại nha :)
Dùng phương pháp nhẩm nghiệm:
x^4+2x^3+x^2+x+1=(x^4+x^3)+(x^3+x^2)+(x+1)=(x+1)(x^3+x^2+1)
\(3x^2-8x+4\)
\(=3x^2-6x-2x+4\)
\(=\left(3x^2-6x\right)-\left(2x-4\right)\)
\(=3x\left(x-2\right)-2\left(x-2\right)\)
\(=\left(3x-2\right)\left(x-2\right)\)
a) \(3x^2-8x-4\)
\(=3x^2-6x-2x+4\)
\(=3x\left(x-2\right)-2\left(x-2\right)\)
\(=\left(x-2\right)\left(3x-2\right)\)
b) \(4x^4+81\)
\(=x^4+81+18x^2-18x^2\)
\(=\left[\left(x^2\right)^2+2x^2.9+9^2\right]-18x^2\)
\(=\left(x^2+9\right)^2-(\sqrt{18}x^2)\)
\(=\left(x^2+9-\sqrt{18}x\right)\left(x^2+9+\sqrt{18}x\right)\)
2x2+3x-5
<=> 2x2+5x-2x-5
<=>(2x2+5x)-(2x+5)
<=>x(2x+5)-1(2x+5)
<=> (x-1)(2x+5)
\(x^2-x-12\)
\(=x^2+3x-4x-12\)
\(=x\left(x+3\right)-4\left(x+3\right)\)
\(=\left(x+3\right)\left(x-4\right)\)
\(x^2-x-12\)
\(\Leftrightarrow x^2-2\frac{1}{2}x+\frac{1}{4}-\frac{49}{4}\)
\(\Leftrightarrow\left(x-\frac{1}{2}\right)^2-\frac{49}{4}\)
\(\Leftrightarrow\left(x-\frac{1}{2}-\frac{7}{2}\right)\left(x-\frac{1}{2}+\frac{7}{2}\right)\)
\(\Leftrightarrow\left(x-4\right)\left(x+3\right)\)
\(x^8+3x^4+4\)
\(=\left(x^8-x^6+2x^4\right)+\left(x^6-x^4+2x^2\right)+\left(2x^4-2x^2+4\right)\)
\(=x^4\left(x^4-x^2+2\right)+x^2\left(x^4-x^2+2\right)+2\left(x^4-x^2+2\right)\)
\(=\left(x^4+x^2+2\right)\left(x^4-x^2+2\right)\)
\(4x^4+4x^3+5x^2+2x+1\)
\(=\left(4x^4+2x^3+2x^2\right)+\left(2x^3+x^2+x\right)+\left(2x^2+x+1\right)\)
\(=2x^2\left(2x^2+x+1\right)+x\left(2x^2+x+1\right)+\left(2x^2+x+1\right)\)
\(=\left(2x^2+x+1\right)^2\)
\(3x^2-13x+10=3x^2-3x-10x+10=3x\left(x-1\right)-10\left(x-1\right)=\left(x-1\right)\left(3x-10\right)\)
\(x^2-x-\dfrac{15}{4}=\left(x^2-x+\dfrac{1}{4}\right)-4=\left(x-\dfrac{1}{2}\right)^2-2^2=\left(x-\dfrac{5}{2}\right)\left(x+\dfrac{3}{2}\right)\)
a, 3x2 - 13x +10
= 3x2 - 3x - 10x + 10
= 3x(x - 1) - 10(x - 1)
= (3x - 10)(x - 1)
b, x2 - x - \(\dfrac{15}{4}\)
= (x2 - 2.\(\dfrac{1}{2}\).x + \(\dfrac{1}{4}\)) - 4
= (x - \(\dfrac{1}{2}\))2 - 22
= ( x - \(\dfrac{1}{2}\) + 2)(x - \(\dfrac{1}{2}\) - 2)
\(81.x^2+4\)
\(=81.\left(x^2+2^2\right)\)
\(=81.\left(x+2\right)\left(x-2\right)\)
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