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(x2 + x)2 - 2(x2 + x) - 15
= [(x2 + x)2 - 2(x2 + x) + 1] - 16
= (x2 + x + 1)2 - 42
= (x2 + x + 5)(x2 + x - 3)
( x2 + x )2 - 2 ( x2 + x ) - 15
Đặt t = x2 + x , đa thức trở thành
t2 - 2t - 15
= ( t2 + 3t ) - ( 5t + 15 )
= t ( t + 3 ) - 5 ( t + 3 )
= ( t - 5 ) ( t + 3 )
= ( x2 + x - 5 ) ( x2 + x + 3 )
x2 + xy + 5x + 5y = ( x2 + xy ) + ( 5x + 5y ) = x( x + y ) + 5( x + y ) = ( x + y )( x + 5 )
x2 - y2 + 3x - 3y = ( x2 - y2 ) + ( 3x - 3y ) = ( x - y )( x + y ) + 3( x - y ) = ( x - y )( x + y + 3 )
x² + xy + 5x + 5y
= (x²+ xy) + ( 5x+5y)
= x(x+y) + 5(x+y)
= (x+y)(x+5)
x² - y² + 3x - 3y
= (x² - y²) + ( 3x -3y)
= (x-y)(x+y) + 3(x-y)
= (x-y)(x+y+3)
chúc bạn học tốt ^^
1/ = x4 + 2x3 + 4x2 + 3x - 10 = (x4 - x3) + (3x3 - 3x2) + (7x2 - 7x) + (10x - 10)
= (x - 1)(x3 + 3x2 + 7x + 10) = (x - 1)[(x3 + 2x2) + (x2 + 2x) + (5x + 10)]
= (x - 1)(x + 2)(x2 + x + 5)
2/ = (x5 - 2x4) + (x4 - 2x3) + (x3 - 2x2) + (x2 - 2x) + (x - 2) = (x - 2)(x4 + x3 + x2 + x + 1)
a) 1/2(x3+8)=1/2(x+2)(x2-2x+4)
b) x4(x-y)+2x3(x-y)=x3(x+2)(x-y)
c) x2-(y2-6y+9)=x2-(y-3)2=(x-y+3)(x+y-3)
d) xy(x3+y3)=xy(x+y)(x2-xy+y2)
e)3x2(x2-25y2)=3x2(x-5y)(x+5y)
f) 4x4+4x2y2+y4-4x2y2= (2x2+y2)2-(2xy)2=(2x2-2xy+y2)(2x2+2xy+y2)
a) \(\frac{1}{2}x^3+4=\frac{1}{2}\left(x^3+8\right)=\frac{1}{2}\left(x+2\right)\left(x^2-2x+4\right)\)
b) \(x^5-x^4y+2x^4-2x^3y=x^3\left(x^2-xy+2x-2y\right)=x^3\left[x\left(x-y\right)+2\left(x-y\right)\right]=x^2\left(x-y\right)\left(x+2\right)\)
c) \(x^2-y^2+6y-9=x^2-\left(y-3\right)^2=\left(x+y-3\right)\left(x-y+3\right)\)
d) \(x^4y+xy^4=xy\left(x^3+y^3\right)=xy\left(x+y\right)\left(x^2-xy+y^2\right)\)
e) \(3x^4-75x^2y^2=3x^2\left(x^2-25y^2\right)=3x^2\left(x+5y\right)\left(x-5y\right)\).
f) \(4x^4+y^4=\left(2x^2+y^2\right)^2-\left(2xy\right)^2=\left(2x^2+y^2+2xy\right)\left(2x^2-y^2-2xy\right)\)
Mình nghĩ là đề thiếu đó bạn :)
đề đáng lẽ phải là: \(x^7+x^2+1\)
\(x^7+x^2+1=\left(x^7-x\right)+\left(x^2+x+1\right)\)
\(=x\left(x^6-1\right)+\left(x^2+x+1\right)\)
\(=x\left(x^3-1\right)\left(x^3+1\right)+\left(x^2+x+1\right)\)
\(=x\left(x-1\right)\left(x^2+x+1\right)\left(x^3+1\right)+\left(x^2+x+1\right)\)
\(=\left[x\left(x-1\right)\left(x+3\right)+1\right]\left(x^2+x+1\right)\)
\(=\left[\left(x^2-x\right)\left(x^3+1\right)+1\right]\left(x^2+x+1\right)\)
\(=\left(x^5-x^4-x^2-x+1\right)\left(x^2+x+1\right)\)
1, = 6(x^2 .y -z^2 +10x+25 )
2, = x^2 -2x-9x+18
= x(x-2)-9(x-2)
= (x-9)(x-2)
a)\(x^4+x^3+x+1=x^3\left(x+1\right)+\left(x+1\right)=\left(x+1\right)\left(x^3+1\right)=\left(x+1\right)^2\left(x^2-x+1\right)\)
b)\(x^4-x^3-x^2+1=\left(x^4-x^3\right)-\left(x^2-1\right)=x^3\left(x-1\right)-\left(x-1\right)\left(x+1\right)\)
\(=\left(x-1\right)\left(x^3-x-1\right)\)
c)\(x^2y+xy^2-x-y=xy\left(x+y\right)-\left(x+y\right)=\left(xy-1\right)\left(x+y\right)\)
\(\dfrac{xy}{2}-x+\dfrac{x^2}{4}=x\left(\dfrac{y}{2}-1+\dfrac{x}{4}\right)\)