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\(x^2-2xy+y^2-z^2=\left(x-y\right)^2-z^2=\left(x-y-z\right)\left(x-y+z\right)\)
\(3x^2+6xy+3y^2-3z^2=3\left(x^2+2xy+y^2-z^2\right)=3.\left[\left(x+y\right)^2-z^2\right]=3.\left(x+y-z\right)\left(x+y+z\right)\)
\(3x^2-3xy-5x+5y=3x\left(x-y\right)-5\left(x-y\right)=\left(x-y\right)\left(3x-5\right)\)
Bài làm :
\(\text{a)}9\left(x+y-1\right)^2-4\left(2x+3y+1\right)^2\)
\(=\left(3x+3y-3\right)^2-\left(4x+6y+2\right)^2\)
\(=\left(3x+3y-3-4x-6y-2\right)\left(3x+3y-3+4x+6y+2\right)\)
\(=\left(-x-3y-5\right)\left(7x+9y-1\right)\)
\(\text{b)}3x^4y^2+3x^3y^2+3xy^2+3y^2\)
\(=\left(3x^4y^2+3xy^2\right)+\left(3x^3y^2+3y^2\right)\)
\(=3xy^2\left(x^3+1\right)+3y^2\left(x^3+1\right)\)
\(=\left(3xy^2+3y^2\right)\left(x^3+1\right)\)
\(=3y^2\left(x+1\right)\left(x+1\right)\left(x^2-x+1\right)\)
\(=3y^2\left(x+1\right)^2\left(x^2-x+1\right)\)
\(\text{c)}\left(x+y\right)^3-1-3xy\left(x+y-1\right)\)
\(=\left(x+y-1\right)\left[\left(x+y\right)^2+x+y+1\right]-3xy\left(x+y-1\right)\)
\(=\left(x+y-1\right)\left(x^2+2xy+y^2+x+y+1-3xy\right)\)
\(=\left(x+y-1\right)\left(x^2+x+y^2+y+1-xy\right)\)
\(d ) x^3+3x^2+3x+1-27z^3\)
\(=\left(x+1\right)^3-\left(3z\right)^3\)
\(=\left(x+1-3z\right)\left(x^2+2x+1+3xz+3z+9z^2\right)\)
Phân tích đa thức thành nhân tử:
\(3x^2-12x^2y^2+3y^2+6xy\)
\(=3\left(x^2-4x^2y^2+y^2+2xy\right)\)
\(=3\left[\left(x^2+2xy+y^2\right)-\left(2xy\right)^2\right]\)
\(=3\left[\left(x+y\right)^2-\left(2xy\right)^2\right]\)
\(=3\left(x+y-2xy\right)\left(x+y+2xy\right)\)
\(3x^2-3y^2-2\left(x-y\right)^2\)
\(=3x^2-3y^2-2\left(x^2-2xy+y^2\right)\)
\(=3x^2-3y^2-2x^2+4xy-2y^2\)
\(=x^2+4xy-5y^2\)
\(=x^2+4xy+4y^2-9y^2\)
\(=\left(x+2y\right)^2-\left(3y\right)^2\)
\(=\left(x+2y-3y\right)\left(x+2y+3y\right)\)
\(=\left(x-y\right)\left(x+5y\right)\)
\(3x^2-5xy-3y^2\)
\(\text{ Phân tích thành nhân tử}\)
\(-\left(3y^2+5xy-3x^2\right)\)
Chúc bạn học tốt
\(3y^3+6xy^2+3x^2y=3y\left(y^2+2xy+x^2\right)=3y\left(x+y\right)^2\)
\(x^3-3x^2-4x+12=x^2\left(x-3\right)-4\left(x-3\right)=\left(x-3\right)\left(x^2-4\right)=\left(x-3\right)\left(x-2\right)\left(x+2\right)\)
\(x^3+3x^2-3x-1=\left(x-1\right)\left(x^2+x+1\right)+3x\left(x-1\right)=\left(x-1\right)\left(x^2+x+1+3x\right)\)
\(=\left(x-1\right)\left(x^2+4x+1\right)\)
Tham khảo nhé~
\(3x^4y^2+3x^3y^2+3xy^2+3y^2=3x^3y^2\left(x+1\right)+3y^2\left(x+1\right)\)
\(=\left(3x^3y^2+3y^2\right)\left(x+1\right)=3y^2\left(x^3+1\right)\left(x+1\right)\)
\(=3y^2\left(x+1\right)\left(x^2-x+1\right)\left(x+1\right)=3y^2\left(x^2-x+1\right)\left(x+1\right)^2\)