Phân tích các đa thức sau thành nhân tử:
a) (x^2+x+1)(x^2+x+2)
b) (x+2)(x+3)(x+4)(x+5)-24
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1)
\((x+2)(x+3)(x+4)(x+5)-24\\=[(x+2)(x+5)]\cdot[(x+3)(x+4)]-24\\=(x^2+7x+10)(x^2+7x+12)-24\)
Đặt \(x^2+7x+10=y\), khi đó biểu thức trở thành:
\(y(y+2)-24\\=y^2+2y-24\\=y^2+2y+1-25\\=(y+1)^2-5^2\\=(y+1-5)(y+1+5)\\=(y-4)(y+6)\\=(x^2+7x+10-4)(x^2+7x+10+6)\\=(x^2+7x+6)(x^2+7x+16)\)
2) Bạn xem lại đề!
\(x^2-4x+3=x^2-3x-x+3=x\left(x-3\right)-\left(x-3\right)=\left(x-1\right)\left(x-3\right)\)
\(x^2+5x+4=x^2+4x+x+4=x\left(x+4\right)+\left(x+4\right)=\left(x+1\right)\left(x+4\right)\)
\(x^2-x-6=x^2-3x+2x-6=x\left(x-3\right)+2\left(x-3\right)=\left(x+2\right)\left(x-3\right)\)
\(x^4+4=\left(x^2\right)^2+2.x^2.2+2^2-4x^2=\left(x^2+2\right)^2-4x^2=\left(x^2+2\right)^2-\left(2x^2\right)=\left(x^2+2+2x\right)\left(x^2-2-2x\right)\)
a) \(3\left(x-y\right)^2+9y\left(y-x\right)^2\)
\(=3\left(x-y\right)^2+9y\left(x-y\right)^2\)
\(=\left(x-y\right)^2\left(3-9y\right)\)
\(=3\left(x-y\right)^2\left(3y+1\right)\)
b) \(3\left(x-y\right)^2+9y\left(y-x\right)\)
\(=3\left(y-x\right)^2+9y\left(y-x\right)\)
\(=\left(y-x\right)\left[3\left(y-x\right)+9y\right]\)
\(=3\left(y-x\right)\left(y-x+3y\right)\)
\(=3\left(y-x\right)\left(4y-x\right)\)
a: =3(x-y)^2+9y(x-y)^2
=(x-y)^2(3+9y)
=(x-y)^2*3*(y+3)
b: =3(x-y)^2-9y(x-y)
=3(x-y)(x-y-9y)
=3(x-y)(x-10y)
a: =(x-z)(y+8)
b; =x^2-2x-3x+6
=(x-2)(x-3)
c: =x^4+10x^2-x^2-10
=(x^2+10)(x^2-1)
=(x^2+10)(x-1)(x+1)
\(a,\left(x-1\right)^2-2^2=\left(x-1-2\right)\left(x-1+2\right)=\left(x-3\right)\left(x+1\right)\\ b,=\left(2x\right)^2+2.2x.3+3^2\\ =\left(2x+3\right)^2\\ c,=x^3-\left(2y\right)^3\\ =\left(x-2y\right)\left(x^2+2xy+4y^2\right)\\ d,=x^3\left(x^2-1\right)-\left(x^2-1\right)\\ =\left(x^3-1\right)\left(x^2-1\right)\\ =\left(x-1\right)\left(x^2+x+1\right)\left(x-1\right)\left(x+1\right)\\ =\left(x-1\right)\left(x+1\right)\left(x^2+x+1\right)\)
\(e,=-4x^2\left(x-1\right)+\left(x-1\right)\\ =\left(1-4x^2\right)\left(x-1\right)\\ =\left(1-2x\right)\left(1+2x\right)\left(x-1\right)\)
\(f,=\left(2x\right)^3+3.\left(2x\right)^2.1+3.2x.1^2+1^3\\ =\left(2x+1\right)^3\)
a: \(4x^2-4x\)
\(=4x\cdot x-4x\cdot1\)
\(=4x\left(x-1\right)\)
b: \(x^2-2xy+y^2-4\)
\(=\left(x-y\right)^2-2^2\)
\(=\left(x-y-2\right)\left(x-y+2\right)\)
\(\left(x^2+x\right)^2-2x^2-2x-15\)
\(=\left(x^2+x\right)^2-\left(2x^2+2x+15\right)\)
\(=\left(x^2+x\right)^2-\left[\left(2x^2+2x\right)+15\right]\)
\(=\left(x^2+x\right)^2-\left[2.\left(x^2+x\right)+15\right]\)
\(=\left(x^2+x\right)^2-2\left(x^2+x\right)-15\) \(\left(1\right)\)
đặt \(x^2+x=t\)
\(\left(1\right)\)\(=\) \(t^2-2t-15\)
\(=\left(t-1\right)^2-16\)
\(=\left(t-1-4\right)\left(t-1+4\right)\)
\(=\left(t-5\right)\left(t+3\right)\)
thay \(t=x^2+x\) ta có
\(\left(1\right)=\left(x^2+x-5\right)\left(x^2+x+3\right)\)
các câu còn lại tương tự nha
học tốt
\(a,=2x\left(x+3\right)\\ b,=x^3\left(x+3\right)+\left(x+3\right)=\left(x^3+1\right)\left(x+3\right)\\ =\left(x+1\right)\left(x+3\right)\left(x^2-x+1\right)\\ c,=64-\left(x-y\right)^2=\left(8-x+y\right)\left(8+x-y\right)\\ A=x^2+6x+5+x^3-8-x^2-x+2\\ A=x^3+5x-1\)
a) 2x2+6x=2x(x+3)
b) x4+3x3+x+3=(x4+x)+(3x3+3)=x(x3+1)+3(x3+1)=(x+3)(x3+1)
c) 64-x2-y2+2xy=-(x2-2xy+y2)+82=8-(x+y)2=(8+x+y)(8-x-y)
A= (x+5)(x+1)+(x-2)(x2+2xx+4)-(x2+x-2)
A= x2+6x+5+x3-8-x2-x+2
A= x3+(x2-x2)+(6x-x)+(5-8+2)
A= x3+5x-1
a) Nó là nhân tử rồi phân tích chi nữa ... Đề thiếu chắc rồi
b) ( x + 2 )( x + 3 )( x + 4 )( x + 5 ) - 24
= [ ( x + 2 )( x + 5 ) ][ ( x + 3 )( x + 4 ) ] - 24
= ( x2 + 7x + 10 )( x2 + 7x + 12 ) - 24
= [ ( x2 + 7x + 11 ) - 1 ][ ( x2 + 7x + 11 ) + 1 ] - 24
= ( x2 + 7x + 11 )2 - 12 - 24
= ( x2 + 7x + 11 )2 - 25
= ( x2 + 7x + 11 )2 - 52
= ( x2 + 7x + 11 - 5 )( x2 + 7x + 11 + 5 )
= ( x2 + 7x + 6 )( x2 + 7x + 16 )
= ( x2 + x + 6x + 6 )( x2 + 7x + 16 )
= [ x( x + 1 ) + 6( x + 1 ) ]( x2 + 7x + 16 )
= ( x + 1 )( x + 6 )( x2 + 7x + 16 )