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\(\left(x^2-2x+3\right)\left(\dfrac{1}{2}x-5\right)\)
\(=\dfrac{1}{2}x^3-x^2+\dfrac{3}{2}x-5x^2+10x-15\)
\(=\dfrac{1}{2}x^3-6x^2+\dfrac{23}{2}x-15\)
\(\left(x^2-2x+3\right)\left(\dfrac{1}{2}x-5\right)\)
\(=\dfrac{1}{2}x^3-5x^2-x^2+10x+\dfrac{3}{2}x-15\)
\(=\dfrac{1}{2}x^3-6x^2+\dfrac{23}{2}x-15\)
[(x2-2xy+2xy2).(x+2y)-(x2+4y2).(x-y)]2xy
=( x3 + 2x2y-2x2y-4xy2+2x2y2+4xy3-x3+x2y-4xy2+4y3 )2xy
=2xy(2x2y2-8xy2+4xy3+x2y+4y3)
= 4x3y3-16x2y3+8x2y4+2x3y2+8xy4
Trả lời:
[ ( x2 - 2xy + 2xy2 ) ( x + 2y ) - ( x2 + 4y2 ) ( x - y ) ] 2xy
= [ ( x3 + 2x2y - 2x2y - 4xy2 + 2x2y2 + 4xy3 ) - ( x3 - x2y + 4xy2 - 4y3 ) ] 2xy
= ( x3 + 2x2y - 2x2y - 4xy2 + 2x2y2 + 4xy3 - x3 + x2y - 4xy2 + 4y3 ) 2xy
= ( x2y - 8xy2 + 2x2y2 + 4xy3 + 4y3 ) 2xy
= 2x3y2 - 16x2y3 + 4x3y3 + 8x2y4 + 8xy4
1, = [(x-1)^2-y^2] : (x-y-1)
= (x+y-1).(x-y-1) : (x-y-1) = x+y-1
2, x^2-x-y^2+y = (x^2-y^2)-(x-y) = (x-y).(x+y) - (x-y) = (x-y).(x+y+1)
k mk nha
\(P=\left(x-y\right)^2+\left(x+y\right)^2-2\left(x+y\right)\left(x-y\right)-4x^2=\left(x-y-x-y\right)^2-\left(2x\right)^2=\left(-2y\right)^2-\left(2x\right)^2\)
\(=\left(2y-2x\right)\left(2y+2x\right)=2\left(y-x\right)2\left(y+x\right)=4\left(x+y\right)\left(y-x\right)\)
\(x^3-x^2y+3x-3y=x^2\left(x-y\right)+3\left(x-y\right)=\left(x-y\right)\left(x^2+3\right)\)
\(x^3-2x^2-4xy^2+x=x\left(x^2-2x+1-4y^2\right)=x\left[\left(x-1\right)^2-\left(2y\right)^2\right]=x\left(x+2y-1\right)\left(x-2y-1\right)\)
\(\left(x+2\right)\left(x+3\right)\left(x+4\right)\left(x+5\right)-8=\left(x^2+7x+10\right)\left(x^2+7x+12\right)-8\)
Đặt \(x^2+7x+10=t\), ta có:
\(t\left(t+2\right)-8=t^2+2t-8=t^2-2t+4t-8=t\left(t-2\right)+4\left(t-2\right)=\left(t-2\right)\left(t+4\right)\)
\(=\left(x^2+7x+10+4\right)\left(x^2+7x+10-2\right)=\left(x^2+7x+14\right)\left(x^2+7x-8\right)\)
a) x(x – y) + y (x + y) = x2 – xy +yx + y2= x2+ y2
với x = -6, y = 8 biểu thức có giá trị là (-6)2 + 82 = 36 + 64 = 100
b) x(x2 – y) – x2 (x + y) + y (x2– x) = x3 – xy – x3 – x2y + yx2 – yx= (2x-2y) – (x2 -2xy +y2) =2(x-y) – (x-y)2
Với x =1/2, y = -100 biểu thức có giá trị là -2 . 1/2. (-100) = 100.
a) x(x – y) + y (x + y) = x2 – xy +yx + y2= x2+ y2
với x = -6, y = 8 biểu thức có giá trị là (-6)2 + 82 = 36 + 64 = 100
b) x(x2 – y) – x2 (x + y) + y (x2– x) = x3 – xy – x3 – x2y + yx2 – yx= (2x-2y) – (x2 -2xy +y2) =2(x-y) – (x-y)2
Với x = \(\frac{1}{2}\), y = -100 biểu thức có giá trị là -2 . \(\frac{1}{2}\). (-100) = 100.
\(2.A=x\left(x^2-y\right)-x^2\left(x+y\right)+y\left(x^2-x\right)=x^3-xy-x^3-x^2y+x^2y-xy=-2xy\\ Thayx=\frac{1}{2};y=-100vàoAđược:A=-2.\frac{1}{2}.\left(-100\right)=100\)
\(3.x\left(5-2x\right)+2x\left(x-1\right)=15\Leftrightarrow5x-2x^2+2x^2-2x=15\Leftrightarrow3x=15\Leftrightarrow x=5\)
a)\(\left(3x^2+2xy\right).\left(5xy^2-4x+\frac{1}{3}y^2\right)\)
\(=15x^3y^2-12x^3+x^2y^3+10x^2y^3-8x^2y+\frac{2}{3}xy^4\)
\(=15x^3y^2-12x^3+11x^2y^3-8x^2y+\frac{2}{3}xy^4\)
b)\(\left(x^3-x^2-7x+3\right):\left(x-3\right)\)
\(=\left(x^3-3x^2+2x^2-6x-x+3\right):\left(x-3\right)\)
\(=\left[x^2\left(x-3\right)+2x\left(x-3\right)-\left(x-3\right)\right]:\left(x-3\right)\)
\(=\left(x-3\right)\left(x^2+2x-1\right):\left(x-3\right)\)
\(=x^2+2x-1\)
\(\left(x^2-3xy\right)\left(x+y\right)\)
\(=x^3+x^2y-3x^2y-3xy^2\)
\(=x^2-2x^2y-3xy^2\)
\(\left(x^2-3xy\right)\left(x+y\right)\)
\(=x^3-x^3y-3xy^2\)
\(=x^2-2x^2y-3xy^2\)