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a) (x2-y2)+(2x+2y)
= (x-y)(x+y)+2(x+y)
= (x+y)(x-y+2)
b) (3a2-6ab+3b2)-12c2
= 3(a2-2ab+b2)-12c2
= 3(a-b)2-3.(2c)2
= 3[(a-b)2-(2c)2]
= 3(a-b-2c)(a-b+2c)
c) (x2+2xy+y2)-25
= (x+y)2-25=(x+y-5)(x+y+5)
d) 81x2-(z2+6yz+9y2)=(9x)2-(z+3y)2=(9x-z-3y)(9x+z+3y)
Bài dễ muốn chết mà giải không được. Chắc do đến Tết lười nè! Nói chơi thôi chứ ai mà không như vậy.
a) \(x^2-y^2+2x+2y=\left(x+y\right)\left(x-y\right)+2\left(x+y\right)=\left(x+y\right)\left(x-y+2\right)\).
b) \(3a^2-6ab+3b^2-12c^2=3\left(a^2-2ab+b^2-4c^2\right)=3\left[\left(a^2-2ab+b^2\right)-4c^2\right]\)
\(=3\left[\left(a-b\right)^2-\left(2c\right)^2\right]=3\left(a-b+2c\right)\left(a-b-2c\right)\).
c) \(x^2-25+y^2+2xy=\left(x^2+2xy+y^2\right)-25=\left(x+y\right)^2-5^2\)
\(=\left(x+y+5\right)\left(x+y-5\right)\).
d) \(81x^2-6yz-9y^2-z^2=81x^2-\left(9y^2+6yz+z^2\right)\)
\(=81x^2-\left[\left(3y\right)^2+2.3y.z+z^2\right]=\left(9x\right)^2-\left(3y+z\right)^2=\left(9x+3y+z\right)\left(9x-3y-z\right)\).
Mình không biết bạn ở trình độ nào nên mình làm chi tiết như vậy. Khi giải, bạn có thể lược bỏ một số bước nếu bạn thấy không cần thiết.
a ) \(3a^2-6ab+3b^2-12c^2\)
\(=3\left(a^2-2ab+b^2-4c^2\right)\)
\(=3\left[\left(a-b\right)^2-\left(2c\right)^2\right]\)
\(=4\left(a-b-2c\right)\left(a-b+2c\right)\)
b ) \(x^2-25+y^2+2xy\)
\(=\left(x^2+2xy+y^2\right)-25\)
\(=\left(x+y\right)^2-5^2\)
\(=\left(x+y-5\right)\left(x+y+5\right)\)
c )
\(x^2y-x^3-9y+9x\)
\(=x^2\left(y-x\right)-9\left(y-x\right)\)
\(=\left(y-x\right)\left(x^2-9\right)\)
\(=\left(y-x\right)\left(x-3\right)\left(x+3\right)\)
d )\(x^2\left(x-1\right)+16\left(1-x\right)\)
\(=x^2\left(x-1\right)-16\left(x-1\right)\)
\(=\left(x-1\right)\left(x^2-16\right)\)
\(=\left(x-1\right)\left(x-4\right)\left(x+4\right)\)
a. x4+2= (x4+\(2\sqrt{2}x^2+2\)) - \(2\sqrt{2}x^2^{ }\) =
\(\left(x^2+\sqrt{2}\right)^2-2\sqrt{2}x^2=\left(x^2-\sqrt{2\sqrt{2}}x+\sqrt{2}\right)\left(x^2+2\sqrt{2}x+\sqrt{2}\right)\)b. 81x2-(9y2+6yz+z2)=81x2 - (3y+z)2=(9x-3y-z)(9x+3y+z)
\(x^3-x^2-5x+125\)
\(=\left(x+5\right)\left(x^2-5x+25\right)-x\left(x+5\right)\)
\(=\left(x+5\right)\left(x^2-5x+25-x\right)\)
\(=\left(x+5\right)\left(x^2-6x+25\right)\)
\(x^6-x^4-9x^3+9x^2\)
\(=x^4\left(x^2-1\right)-9x^2\left(x-1\right)\)
\(=x^4\left(x-1\right)\left(x+1\right)-9x^2\left(x-1\right)\)
\(=x^2\left(x-1\right)\left[x^2\left(x+1\right)-9\right]\)
\(=x^2\left(x-1\right)\left(x^3+x^2-9\right)\)
\(x^4-4x^3+8x^2-16x+16\)
\(=\left(x^2+4\right)^2-4x\left(x^2+4\right)\)
\(=\left(x^2+4\right)\left(x^2+4-4x\right)\)
\(=\left(x^2+4\right)\left(x-2\right)^2\)
\(3a^2-6ab+3b^2-12c^2\)
\(=3\left(a^2-2ab+b^2-4c^2\right)\)
\(=3\left[\left(a-b\right)^2-\left(2c\right)^2\right]\)
\(=3\left(a-b+2c\right)\left(a-b-2c\right)\)
a) = x2 (y - x) - 9( y - x) = ( y - x ) ( x2 - 9) = ( y -x) ( x - 3 ) ( x + 3)
b) = x2 ( x - 1 ) - 16 ( x - 1 ) = ( x - 1 ) ( x2 - 16 ) = ( x - 1 ) ( x - 4 ) ( x + 4 )
c) = (9x)2 - ( 9y2 + 6yz + z2 ) = (9x)2 - ( 3y + z)2 = (9x - 3y - z ) ( 9x + 3y + z)
d) = z( x - y) - ( x2 -2xy + y2 ) = z(x - y) - (x - y)2 = (x - y) (z - 1)
e) = (x + 3) (x + 5)
f) = (x - 4) ( x + 3)
g) = (9x)2 + 2.9x.2 + 22 - 36x = (9x + 2)2 - (\(6\sqrt{x}\))2 = \(\left(9x+2+6\sqrt{x}\right)\). \(\left(9x+2-6\sqrt{x}\right)\)
a) x2y - x3 - 9y + 9x = x2(y - x) - 9(y - x) = (y - x)(x2 - 9) = (y - x)(x + 3)(x - 3).
b) x2(x - 1) + 16(1 - x) = (x - 1)(x2 - 16) = (x - 1)(x - 4)(x + 4).
c) 81x2 - 6yz - 9y2 - z2 = (9x)2 - ((3y)2 + 2.3yz + z2) = (9x)2 - (3y + z)2 = (9x + 3y +z)(9x - 3y - z).
d) xz - yz - x2 + 2xy - y2 = z(x - y) - (x - y)2 = (x - y)(z - x + y).
e) x2 + 8x + 15 = (x2 + 3x) + (5x + 15) = x(x + 3) + 5(x + 3) = (x + 3)(x + 5).
f) x2 - x - 12 = (x2 - 4x) + (3x - 12) = x(x - 4) + 3(x - 4) = (x - 4)(x + 3).
g) (Đề sai) 81x4 + 4 = (81x4 + 36x2 + 4) - 36x2 = (9x2 + 2)2 - 36x2 = (9x2 + 2 + 6x)(9x2 + 2 - 6x).
\(81x^2-6yz-9y^2-z^2=81x^2-\left(6yz+9y^2+z^2\right)\)
\(=81x^2-\left(9y^2+6xy+z^2\right)=81x^2-\left(3y+z\right)^2\)
\(=\left(9x-3y-z\right)\left(9x+3y+z\right)\)
a)x^3-x+3x^2y+3xy^2+y^3-y
=(x^3+3x^2y+3xy^2+y^3)-(x+y)
=(x+y)^3-(x+y)
=(x+y)[(x+y)^2-1]
=(x+y)(x+y-1)(x+y+1)
b)81x^2-6yz-9y^2-z^2
=81x^2-(9y^2-6yz+z^2)
=81x^2-(3y-z)^2
=(9x)^2-(3y-z)^2
=(9x-3y+z)(9x+3y-z)
c)12x^2-72x+60
=12(x^2-6x+5)
=12(x^2-x-5x+5)
=12[x(x-1)-5(x-1)]
=12(x-1)(x-5)
A.5X2+3(X+Y)2-5Y2
= 5.(x2 - y2) + 3(x+y)2
=5.( x-y).(x+y) +3(x+y)2
= ( x+y).[(5.( x-y) + 3(x+y)]
=( x+y).( 5x-5y +3x + 3y)
=( x+y).( 8x - 2y)
=( x+y).2(4x - y)
C.81x2 - 6yz - 9y2 - z2
=( 9x)2 - (z2 + 6yz+ 9y2)
=( 9x)2 -( z +3y)2
=(9x - z -3y).(9x + z+3y)
D.x2y-x3-9y+9x
=9.(x - y) + x2(y - x)
= 9.(x-y) - x2(x-y)
=(x+y).[32- x2]
=(x+y).(3-x).(x+2)
E.x3+9x2-4x-36
=(x3-4x) + (-36 +9x2)
=x.(x2-4) + 9.(x2-4)
=(x2-4).(x+9)
H.2x3+x2-8x-4
= x2.(2x+1)-4.(2x +1)
=(2x +1).(x2 -4)
= (2x +1).(x-2).(x+2)
Cậu xem trước nhé
a) 3a2-6ab+3b2-12c2
=3.(a2-2ab+b2-4c2)
=3.[(a-b)2-4c2]
=3.(a-b-2c)(a-b+2c)
a)\(81x^2-6yz-9y^2-z^2\)
\(=81x^2-\left(z-3y\right)^2\)
\(=\left(9x-z+3y\right)\left(9x+z-3y\right)\)
b)\(x^2y-x^3-9y+9x\)
\(=x^2\left(y-x\right)-9\left(y-x\right)\)
\(=\left(y-x\right)\left(x-3\right)\left(x+3\right)\)
c)\(3a^2-6ab+3b^2-12c^2\)
\(=3\left(a^2-2ab+b^2-4z^2\right)\)
\(=3\left[\left(a-b\right)^2-4z^2\right]\)
\(=3\left(a-b-2z\right)\left(a-b+2z\right)\)
a)\(81x^2-6yz-9y^2-z^2=\left(9x\right)^2-\left(9y^2+6yz+z^2\right)=\left(9x\right)^2-\left(3y+z\right)^2=\left(9x-3y-z\right)\left(9x+3y+z\right)\)b)\(x^2y-x^3-9y+9x=x^2\left(y-x\right)-9\left(y-x\right)=\left(x^2-9\right)\left(y-x\right)=\left(x-3\right)\left(x+3\right)\left(y-x\right)\)
c)\(3a^2-6ab+3b^2-12c^2=3\left(a^2-2ab+b^2-4c^2\right)=3\left[\left(a-b\right)^2-\left(2c\right)^2\right]=3\left(a-b-2c\right)\left(a-b+2c\right)\)