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1)x(x2 - 19 - 30)
2)x(x2 - 7 - 6)
3)x(x2 + 4x - 7 - 10)
( 4 tích mình làm tiếp 3 câu cuối)
a) 2x + 2y - x2 - xy
= 2(x + y) + x(x + y)
= (x + y) (x + 2)
mk ko bít phân tích đúng ko đúng thì t i c k nhé!! 245433463463564564574675687687856856846865855476457
a)\(2x+2y-x^2-xy=2\left(x+y\right)-x\left(x+y\right)=\left(2-x\right)\left(x+y\right)\)
b)\(\left(x+3\right)^2-\left(2x-5\right)\left(x+3\right)\)
\(=\left(x+3\right)\left[\left(x+3\right)-\left(2x-5\right)\right]\)
\(=\left(x+3\right)\left(8-x\right)\)
c)\(\left(3x+2\right)^2+\left(3x-2\right)^2-2\left(9x^2-4\right)\)
\(=\left(3x+2\right)^2+\left(3x-2\right)^2-2\left(3x-2\right)^2\)
\(=\left(3x+2\right)\left[\left(3x+2\right)-\left(3x-2\right)\right]+\left(3x-2\right)\left[\left(3x-2\right)-\left(3x+2\right)\right]\)
\(=4\left(3x+2\right)-4\left(3x-2\right)\)
\(=4\left(3x+2-3x+2\right)\)
=4.4=16
1,
\(x^2+y^2+z^2=xy+yz+zx\)
\(\Leftrightarrow x^2+y^2+z^2-xy-yz-zx=0\)
\(\Leftrightarrow2x^2+2y^2+2z^2-2xy-2yz-2zx=2.0=0\)
\(\Leftrightarrow\left(x^2-2xy+y^2\right)+\left(y^2-2yz+z^2\right)+\left(z^2-2zx+x^2\right)=0\)
\(\Leftrightarrow\left(x-y\right)^2+\left(y-z\right)^2+\left(z-x\right)^2=0\)
<=> x - y = 0
y - z = 0
z - x =0
<=> x=y
y=z
z=x
<=> x=y=z
1)VD:\(X=Y=Z\Leftrightarrow XY+YZ+ZX=X^2+Y^2+Z^2\)
\(\Leftrightarrow X^2+Y^2+Z^2=XY+YZ+ZX\left(1\right)\)
VD:\(X^2+Y^2+Z^2=XY+YZ+ZX\Leftrightarrow2X^2+2Y^2+2Z^2=2XY+2YZ+2ZX\)
\(\Leftrightarrow2X^2+2Y^2+2Z^2-2XY-2YZ-2ZX=0\)
\(\Leftrightarrow\left(X-Y\right)^2+\left(Y-Z\right)^2+\left(Z-X\right)^2=0\left(HĐT\right)\)
\(\Rightarrow X=Y=Z\left(2\right)\)
\(1\&2\Rightarrow X^2+Y^2+Z^2=XY+YZ+ZX\)
\(\Leftrightarrow X=Y=Z\)
2)\(\Rightarrow A+B+C\Rightarrow X=-\left(Y+Z\right)\Rightarrow X^2=\left(Y+Z\right)^2\)
\(\Leftrightarrow X^2=Y^2+2YZ+Z^2\)
\(\Leftrightarrow X^2-Y^2-Z^2=2YZ\)
\(\Leftrightarrow\left(X^2-Y^2-Z^2\right)^2=4Y^2Z^2\)
\(\Leftrightarrow X^4+Y^4+Z^4=2X^2Y^2+2Y^2Z^2+2Z^2X^2\)
\(\Leftrightarrow2\left(X^4+Y^4+Z^2\right)=\left(X^2+Y^2+Z^2\right)^2=A^4\)
\(\Rightarrow X^4+Y^4+Z^4=\frac{A^4}{2}\)
2(x4+y4+z4)-(x2+y2+z2)2-2(x2+y2+z2)(x+y+z)2+(x+y+z)4
=2(x4+y4+z4)-(x2+y2+z2)2+(x+y+z)2[-2(x2+y2+z2)+(x+y+z)2]
tới đây r` sao đặt ẩn phân tích tiếp chắc =="
d) ax2 + ay - bx2 - by
= ( ax2 + ay ) - ( bx2 + by )
= a ( x2 + y ) - b ( x2 + y )
= ( x2 + y )( a - b )
c) x2y + xy2 - x - y
= ( x2y + xy2 ) - ( x + y )
= xy ( x + y ) - ( x+ y )
= ( x + y ) ( xy - 1 )
\(xy\left(x-y\right)+yz\left(y-z\right)+zx\left(z-x\right)=x^2y-xy^2+y^2z-yz^2+z^2z-zx^2=x^2\left(y-z\right)+y^2\left(z-x\right)+z^2\left(z-y\right)\)
\(x^2\left(y-z\right)-y^2\left(x-z\right)-z^2\left(y-z\right)=\left(y-z\right)\left(x-z\right)\left(x+z\right)-y^2\left(x-z\right)=\left(x-z\right)\left(xy-yz-zx-z^2-y^2\right)\)
t cx k bt có đúng hay k đâu nha, nhớ xem kĩ lại
Cảm ơn nhiều nhé =))