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b) \(3x\left(x-1\right)^2-2x\left(x+3\right)\left(x-3\right)+4x\left(x-4\right)\)
\(=3x\left(x^2-2x+1\right)-2x\left(x^2-9\right)+4x^2-16x=3x^3-6x^2+3x-2x^3+18x+4x^2-16x\)\(=x^3-2x^2+5x\)
c) \(2\left(2x+5\right)^2-3\left(4x+1\right)\left(1-4x\right)=2\left(4x^2+20x+25\right)+3\left(16x^2-1\right)\)
\(=8x^2+40x+50+48x^2-3=56x^2+40x+47\)
d) \(x\left(x+4\right)\left(x-4\right)-\left(x^2+1\right)\left(x^2-1\right)=x\left(x^2-16\right)-x^4+1=x^3-x^4-16x+1\)
e) \(\left(y-3\right)\left(y+3\right)\left(y^2+9\right)-\left(y^2+2\right)\left(y^2-2\right)=\left(y^2-9\right)\left(y^2+9\right)-y^4+4=y^4-81-y^2+4=-77\)
Mạn phép bỏ câu a :))
b) a2(b2 - a2) + b2(b2 + a2)
= a2.b2 + a2.(-a2) + b2.b2 + b2.a2
= a2.b2 - a4 + b4 + a2.b2
= a4 + 2a2b2 + b2 (hđt)
c) x2(x3 + 2y - x2y) - y(x2 - x4 + y)
= x2.x3 + x2.2y + x2.(-x2y) + (-y).x2 + (-y).(-x)4 + (-y).y
= x5 + 2x2y - x4y - x2y + x4y - y2
= x5 + (2xy2 - xy2) + (-x4y + x4y) - y2
= x5 + xy2 - y2
a, x3 - x2 - x + 1
= x\(^2\) ( x - 1 ) - (x - 1 )
= ( x\(^2\) - 1 ) (x - 1 )
b, x2y2 + 1 - x2 - y2
= ( \(x^2y^2\) - \(x^2\) ) - ( \(y^2\) - 1 )
= \(x^2\) ( \(y^2-1\)) - ( \(y^2-1\) )
= ( \(x^2-1)\left(y^2-1\right)\)
c, x4 - x2 + 2x - 1
= \(x^4\) - (\(x^2\) - 2x + 1 )
= (x\(^2\))\(^2\) - (x - 1 )\(^2\)
= ( x\(^2\) - x + 1 ) (x\(^2\) + x -1 )
e, x2 - y2 - 2x - 2y
= (x - y ) ( x + y ) - 2 ( x + y )
= ( x - y - 2 ) ( x+ y )
f, x2 - y2 + 2y - 1
= x\(^2\) - ( y\(^2\) - 2y + 1 )
= x\(^2\) - ( y - 1 )\(^2\)
= (x - y +1 ) ( x+y - 1)
a/ \(\left(x-2y\right)^2+3\left(x-2y\right)\left(x+2y\right)\)
\(=\left(x-2y\right)\left(x-2y+3x-6y\right)=\left(x-2y\right)\left(4x-8y\right)\)
\(=4\left(x-2y\right)\left(x-2y\right)=4\left(x-2y\right)^2\)
b/ \(\left(y^2+1\right)\left(y+2\right)-\left(y+2\right)\left(y^2-2y+4\right)\)
\(=y^3+2y^2+y+2-y^3-8\)
\(=2y^2+y-6=2y^2+4y-3y-6\)
\(=\left(y+2\right)\left(2y-3\right)\)
riêng câu b mình có sửa đề lại, bn xem có đúng hong nha. Chúc bn hc tốt nhé ^^
a) Mình không hiểu đề cho lắm 
b) \(3x\left(x-1\right)^2-2x\left(x+3\right)\left(x-3\right)+4x\left(x-4\right)\)
\(=3x\left(x^2-2x+1\right)-2x\left(x^2-9\right)+4x\left(x-4\right)\)
\(=3x^3-6x^2+3x-2x^3+18x+4x^2-16x\)
\(=x^3-2x^2+5x\)
c) \(2\left(2x+5\right)^2-3\left(4x+1\right)\left(1-4x\right)\)
\(=2\left(2x+5\right)^2+3\left(4x+1\right)\left(4x-1\right)\)
\(=2\left(4x^2+20x+25\right)+3\left(16x^2-1\right)\)
\(=8x^2+40x+50+48x^2-3\)
\(=56x^2+40x+47\)
d) \(x\left(x+4\right)\left(x-4\right)-\left(x^2+1\right)\left(x^2-1\right)\)
\(=x\left(x^2-16\right)-\left(x^4-1\right)\)
\(=x^3-16x-x^4+1\)
e) \(\left(y-3\right)\left(y+3\right)\left(y^2+9\right)-\left(y^2+2\right)\left(y^2-2\right)\)
\(=\left(y^2-9\right)\left(y^2+9\right)-\left(y^4-4\right)\)
\(=y^4-81-y^4+4\)
\(=-77\)
a/ (x+y)3-(x-y)3-2y3
= (x3+3x2y+3xy2+y3)-(x3-3x2y+3xy2-y3)-2y3
= x3+3x2y+3xy2+y3-x3+3x2y-3xy2+y3-2y3
= 6xy2
b/ (x+2)(x2-2x+4)-(16-x3)
= x3-2x2+4x+2x2-4x+8-16+x3
= 2x3-8
c/ (2a+b)(4a2-2ab+b2)-(2a-b)(4a2+2ab+b2)
= (8a3+b3)-(8a3-b3)
= 8a3+b3-8a3+b3
= 2b3