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\(x^4+x^2-2=x^4-x^2+2x^2-2 \)
\(=x^2\left(x^2-1\right)+2\left(x^2-1\right)\)
\(=\left(x^2-1\right)\left(x^2+2\right)\)
\(=\left(x+1\right)\left(x-1\right)\left(x^2+2\right)\)
\(2x^2-8y^2+5xy^2-10y^3\)
\(=2\left(x^2-4y^2\right)+5y^2\left(x-2y\right)\)
\(=2\left(x-2y\right)\left(x+2y\right)+5y^2\left(x-2y\right)\)
\(=\left(2x+4y\right)\left(x-2y\right)+5y^2\left(x-2y\right)\)
\(=\left(x-2y\right)\left(5y^2+2x+4y\right)\)
\(3x^3-12x^2y+12-75xz^2\)
\(=3\left[x^3-4x^2y+4-25xz^2\right]\)
a: x^2+4xy-21y^2
\(=x^2+7xy-3xy-21y^2\)
\(=x\left(x+7y\right)-3y\left(x+7y\right)\)
\(=\left(x+7y\right)\left(x-3y\right)\)
b: \(5x^2+6xy+y^2\)
\(=5x^2+5xy+xy+y^2\)
=5x(x+y)+y(x+y)
=(x+y)(5x+y)
c: \(x^2+2xy-15y^2\)
\(=x^2+5xy-3xy-15y^2\)
=x(x+5y)-3y(x+5y)
=(x+5y)(x-3y)
d: \(x^2-7xy+10y^2\)
\(=x^2-2xy-5xy+10y^2\)
=x(x-2y)-5y(x-2y)
=(x-2y)(x-5y)
a) \(x^2+4xy-21y^2\)
\(=x^2+7xy-3xy-21y^2\)
\(=x\left(x+7y\right)-3y\left(x+7y\right)\)
\(=\left(x+7y\right)\left(x-3y\right)\)
b) \(5x^2+6xy+y^2\)
\(=5x^2+5xy+xy+y^2\)
\(=5x\left(x+y\right)+y\left(x+y\right)\)
\(=\left(5x+y\right)\left(x+y\right)\)
c) \(x^2+2xy-15y^2\)
\(=x^2+5xy-3xy-15y^2\)
\(=x\left(x+5y\right)-3y\left(x+5y\right)\)
\(=\left(x+5y\right)\left(x-3y\right)\)
d) \(x^2-7xy+10y^2\)
\(=x^2-2xy-5xy+10y^2\)
\(=x\left(x-2y\right)-5y\left(x-2y\right)\)
\(=\left(x-5y\right)\left(x-2y\right)\)
\(2x^2y+4xy^2+2y^3-8\)
\(=2y\left(x^2+2xy+y^2\right)-8\)
\(=2y\left(x+y\right)^2-8\)
\(=2\left[y\left(x+y\right)^2-4\right]\)
Đề sai nhé .Sửu lại
\(x^2-4x^2y^2+4+4x\)
\(=\left(x^2+4x+4\right)-4x^2y^2\)
\(=\left(x+2\right)^2-\left(2xy\right)^2\)
\(=\left(x+2+2xy\right)\left(x+2-2xy\right)\)
1) \(3x^3-12x\)
\(=3x\left(x^2-4\right)\)
\(=3x\left(x+2\right)\left(x-2\right)\)
2)\(x^3+x^2-x-1\)
\(=\left(x^3+x^2\right)-\left(x+1\right)\)
\(=\left(x+1\right)\left(x^2-1\right)\)
\(=\left(x+1\right)^2\left(x-1\right)\)
3) \(x^2-7xy+10y^2\)
\(=\left(x^2-2xy\right)-\left(5xy-10y^2\right)\)
\(=x\left(x-2y\right)-5y\left(x-2y\right)\)
\(=\left(x-5y\right)\left(x-2y\right)\)
1) \(3x^3-12x\)
\(=3x\left(x^2-4\right)\)
\(=3x\left(x-2\right)\left(x+2\right)\)
2) \(x^3+x^2-x-1\)
\(=x^2\left(x+1\right)-\left(x+1\right)\)
\(=\left(x^2-1\right)\left(x+1\right)\)
\(=\left(x-1\right)\left(x+1\right)\left(x+1\right)\)