Question

 giải hộ mình câu 17-22

Answer 1

17)\(\left(x+y+z\right)^2-4z^2\)

\(=\left(x+y+z-2z\right)\left(x+y+z+2z\right)\)

\(=\left(x+y-z\right)\left(x+y+3z\right)\)

18)\(x^3y^3+125=\left(xy\right)^3+5^3=\left(xy+5\right)\left(x^2y^2-5xy+25\right)\)

19)\(8x^3-y^3-6xy\left(2x-y\right)\)

\(=\left(2x-y\right)\left(4x^2+2xy+y^2\right)-6xy\left(2x-y\right)\)

\(=\left(2x-y\right)\left(4x^2+2xy+y^2-6xy\right)\)

\(=\left(2x-y\right)\left(4x^2-4xy+y^2\right)\)

\(=\left(2x-y\right)\left(2x-y\right)^2=\left(2x-y\right)^3\)

20)\(-\frac{1}{9}x^2+\frac{1}{3}xy-\frac{1}{4}y^2\)

\(=-\left(\frac{1}{9}x^2-\frac{1}{3}xy+\frac{1}{4}y^2\right)=-\left(\frac{1}{3}x-\frac{1}{2}y\right)^2\)

21)\(x^4y^4-z^4=\left[\left(xy\right)^2\right]^2-\left(z^2\right)^2\)

\(=\left(x^2y^2-z^2\right)\left(x^2y^2+z^2\right)\)

\(=\left(xy-z\right)\left(xy+z\right)\left(x^2y^2+z^2\right)\)