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a) 9x4+16y6-24x2y3
=(3x2)2-2.3x2.4y3+(4y3)2
=(3x2-4y3)2
b) 16x2-24xy+9y2
=(4x)2-2.4x.3y+(3y)2
=(4x-3y)2
c) 36x2-(3x-2)2
=(36x-3x+2)(36x+3x-2)
=(33x+2)(39x-2)
d) 27x3+54x2y+36xy2+8y3
=(3x)3+3.(3x)2.2y+3.3x.(2y)2+(2y)3
=(3x+2y)3
e) y9-9x2y6+27x4y3-27x6
=(y3)3-3.(y3)2.3x2+3.y3.(3x2)2-(3x2)3
=(y3-3x2)3
f) 64x3+1
= (4x)3+13
=(4x+1)[(4x)2-4x.1+12]
=(4x+1)(16x2-4x+1)
e) 27x6-8x3 *sửa đề*
=(3x2)3-(2x)3
=(3x2-2x)[(3x)2+3x2.2x+(2x)2]
=(3x2-2x)(9x2+6x3+4x2)
~~~
a: =(6x)^2-(3x-2)^2
=(6x-3x+2)(6x+3x-2)
=(9x-2)(3x+2)
d: \(=\left[\left(x+1\right)^2-\left(x-1\right)^2\right]\left[\left(x+1\right)^2+\left(x-1\right)^2\right]\)
\(=4x\cdot\left[x^2+2x+1+x^2-2x+1\right]\)
=8x(x^2+1)
e: =(4x)^2-2*4x*3y+(3y)^2
=(4x-3y)^2
f: \(=-\left(\dfrac{1}{4}x^4-2\cdot\dfrac{1}{2}x^2\cdot2y^3+4y^6\right)\)
\(=-\left(\dfrac{1}{2}x^2-2y^3\right)^2\)
g: =(4x)^3+1^3
=(4x+1)(16x^2-4x+1)
k: =x^3(27x^3-8)
=x^3(3x-2)(9x^2+6x+4)
l: =(x^3-y^3)(x^3+y^3)
=(x-y)(x+y)(x^2-xy+y^2)(x^2+xy+y^2)
1) x2 + x - y2 + y = (x2 - y2) + (x + y) = (x - y)(x + y) + (x + y) = (x - y + 1)(x + y)
2) 4x2 - 9y2 + 4x - 6y = (4x2 - 9y2) + (4x - 6y) = (2x - 3y)(2x + 3y) + 2(2x - 3y) = (2x - 3y)(2x + 3y + 2)
3) x2 + x + y2 + y + 2xy = (x2 + 2xy + y2) + (x + y) = (x + y)2 + (x + y) = (x + y)(x + y + 1)
4) -x2 + 5x + 2xy - 5y - y2 = -(x2 - 2xy + y2) + (5x - 5y) = -(x - y)2 + 5(x - y) = (x - y)(y - x + 5)
5) x2 - y2 + 2x + 1 = (x2 + 2x + 1) - y2 = (x + 1)2 - y2 = (x + 1 + y)(x - y + 1)
6) x2 - 1 - y2 + 2y = x2 - (y2 - 2y + 1) = x2 - (y - 1)2 = (x - y + 1)(x + y - 1)
7) x2 + 2xz - y2 + 2uy + z2 - u2 =(x2 + 2xz + z2) - (y2 - 2uy + u2) = (x + z)2 - (y - u)2 = (x + z - y + u)(x + z + y - u)
8) x3 + 3x2y + x + 3xy2 + y + y3 = (x3 + 3x2y + 3xy2 + y3) + (x + y) = (x + y)3 + (x + y) = (x + y)(x2 + 2xy + y2 + 1)
9) x3 + y(1 - 3x2) + x(3y2 - 1) - y3 = x3 + y - 3x2y + 3xy2 - x - y3 = (x3 - 3x2y + 3xy2 - y3) - (x - y) = (x - y)3 - (x - y) = (x - y)(x2 - 2xy+y2-1)
a) \(x^2+2xy^3-3z+4xy-5xy^2+2xy-5z\)
\(=x^2+2xy^3-5xy^2-\left(3z+5z\right)+\left(4xy+2xy\right)\)
\(=x^2+2xy^3-5xy^2-8z+6xy\)
b) \(\left(x-3y\right)\left(x^2-3xy+9y^2\right)\)
\(=\left(x-3y\right)\left[x^2-x\cdot3y+\left(3y\right)^2\right]\)
\(=x^3-\left(3y\right)^3\)
\(=x^3-27y^3\)
c) \(\left(2x-y\right)\left(2x+y\right)\)
\(=\left(2x\right)^2-y^2\)
\(=4x^2-y^2\)
d) \(\left(3x-y\right)\left(2y+5\right)-16x4y\)
\(=6xy+15x-2y^2-5y-64xy\)
\(=-58xy+15x-2y^2-5y\)
a) x^2 - 5xy +4y^2= x^2 -xy -4xy+4y^2= (x^2-xy) - (4xy - 4y^2)= x(x-y)-4y(x-y)=(x-y)*(x - 4y)
b) x^2 -y^4+9y -x(9+y-y^3= x^2-y^4 +9y-9x-xy+xy^3= (x^2-xy)-(9x-9y)+(xy^3-y^4)=x(x-y)-9(x-y)+y^3(x-y)=(x-y)*(y^3+x-9)
d) 2u^2+2v^2-5uv=(2u^2-4uv)+(2v^2-uv)=2u(u-2v)+v(2v-u)= 2u(u-2v)-v(u-2v)=(u-2v)*(2u-v)
a) x2+6xy+9y2=(x+3y)^2
b)4x2-12xy+9y^2=(2x-3y)^2
c)x2-10xy+25y^2=(x-5y)^2
d)9x^2+24xy+16y^2=(3x+4y)^2
e)27x^3+54x2y+36xy2+8y3=(3x+2y)^3
f)x^3-6x^2y+12xy2-8y3=(x-2y)^3
g)8x3+12x^2y+6xy2+y3=(2x+y)^3
h)8x^3-12x2y+6xy2-y^3=(2x-y)^3
a.
\(x^2+4y^2+4xy=0\)
\(\Leftrightarrow\left(x+2y\right)^2=0\)
\(\Leftrightarrow x+2y=0\)
\(\Leftrightarrow x=-2y\)
Vậy pt đã cho có vô số nghiệm dạng \(\left(x;y\right)=\left(-2k;k\right)\) với k là số thực bất kì (nếu đề đúng)
b.
\(2y^4-9y^3+2y^2-9y=0\)
\(\Leftrightarrow2y^2\left(y^2+1\right)-9y\left(y^2+1\right)=0\)
\(\Leftrightarrow\left(2y^2-9y\right)\left(y^2+1\right)=0\)
\(\Leftrightarrow y\left(2y-9\right)\left(y^2+1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}y=0\\2y-9=0\\y^2+1=0\left(vn\right)\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}y=0\\y=\dfrac{9}{2}\end{matrix}\right.\)
c. Em kiểm tra lại đề chỗ \(3xy^2\), đề đúng như vậy thì pt này ko giải được