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\(x^8+3x^4+4\)
\(=\left(x^8-x^6+2x^4\right)+\left(x^6-x^4+2x^2\right)+\left(2x^4-2x^2+4\right)\)
\(=x^4\left(x^4-x^2+2\right)+x^2\left(x^4-x^2+2\right)+2\left(x^4-x^2+2\right)\)
\(=\left(x^4+x^2+2\right)\left(x^4-x^2+2\right)\)
\(4x^4+4x^3+5x^2+2x+1\)
\(=\left(4x^4+2x^3+2x^2\right)+\left(2x^3+x^2+x\right)+\left(2x^2+x+1\right)\)
\(=2x^2\left(2x^2+x+1\right)+x\left(2x^2+x+1\right)+\left(2x^2+x+1\right)\)
\(=\left(2x^2+x+1\right)^2\)
\(x^2-5x+6\)
\(=x^2-5x+\frac{25}{4}-\frac{1}{4}\)
\(=\left(x-\frac{5}{2}\right)^2-\left(\frac{1}{2}\right)^2\)
\(=\left(x-\frac{5}{2}-\frac{1}{2}\right)\left(x-\frac{5}{2}+\frac{1}{2}\right)\)
\(=\left(x-3\right)\left(x-2\right)\)
\(x^2-5x+6 \)
= \(x^2-2x-3x+6\)
= \(\left(x^2-2x\right)-\left(3x-6\right)\)
= \(x\left(x-2\right)-3\left(x-2\right)\)
= \(\left(x-2\right)\left(x-3\right)\)
= x^4 + x^3 + 4x^3 + 4x^2 - 11x^2 - 11x -30x - 3
= x^3 ( x + 1) + 4x^2 ( x + 1)- 11x( x + 1) - 30 ( x+ 1)
= ( x + 1)(x^3 + 4x^2 - 11x - 30)
= ( x + 1) [ x^3 - 3x^2 + 7x^2 - 21x + 10x - 30]
= ( x + 1) [ x^2 ( x - 3) + 7x(x - 3) + 10 ( x- 3) ]
= ( x + 1 ) (x - 3 )(x^2 + 7x + 10)
= ( x + 1)(x - 3) [ x^2 + 2x + 5x + 10)
= ( x+ 1)(x-3) [ x(x+2) + 5(x+2) ]
=(x + 1)(x-3)(x+2)(x+5)
a/ x4 +5x3 +10x-4
=(x4- 4)+(5x3 + 10x)
=(x2+2) (x2-2) + 5x(x2 +2 )
=(x2+2)(x2 -2 +5x)
b/x5 - x4 +x3 -x2 +x-1
=x4(x-1)+x3(x-1)+(x-1)
=(x-1)(x4+x3+1)
a) bt \(=\left(x-8\right)\left(x^2-x-2\right)=\left(x-8\right)\left(x+1\right)\left(x-2\right)\)
kl: ...
b) \(=\left(x+2\right)\left(x^2-8x-15\right)=\left(x+2\right)\left(x-5\right)\left(x-3\right)\)
kl:....
a, \(x^3-9x^2+6x+16\)
\(=x^3-8x^2-x^2+8x-2x+16\)
\(=x^2\left(x-8\right)-x\left(x-8\right)-2\left(x-8\right)\)
\(=\left(x-8\right)\left(x^2-x-2\right)\)
\(=\left(x-8\right)\left(x^2-2x+x-2\right)\)
\(=\left(x-8\right)\left[x\left(x-2\right)+\left(x-2\right)\right]\)
\(=\left(x-8\right)\left(x-2\right)\left(x+1\right)\)
b, \(x^3-6x^2-x+30\)
\(=x^3-5x^2-x^2+5x-6x+30\)
\(=x^2\left(x-5\right)-x\left(x-5\right)-6\left(x-5\right)\)
\(=\left(x-5\right)\left(x^2-x-6\right)\)
\(=\left(x-5\right)\left(x^2-3x+2x-6\right)\)
\(=\left(x-5\right)\left[x\left(x-3\right)+2\left(x-3\right)\right]\)
\(=\left(x-5\right)\left(x-3\right)\left(x+2\right)\)
Chúc bạn học tốt!!!
a) \(x^3-5x^2+8x-4=\left(x^3-x^2\right)-4\left(x^2-x\right)+4\left(x-1\right)=x^2\left(x-1\right)-4x\left(x-1\right)+4\left(x-1\right)\)
\(=\left(x-1\right)\left(x^2-4x+4\right)=\left(x-1\right)\left(x-2\right)^2\)
b) \(A=5x\left(2x-3\right)+4\left(2x-3\right)+7\) chia hết cho 2x-3 => 7 chia hết cho 2x -3
=> 2x -3 thuộc U(7) ={-7;-1;1;7}
+2x-3 =-7 => x =-2
+2x-3 =-1 => x =1
+2x-3 =1 => x =2
+2x -3 =7 => x =5
\(5x^3-40=5\left(x^3-8\right)=5\left(x^3-2^3\right)=5\left(x-2\right)\left(x^2+2x+4\right)\)