Bài `1:`
`a)y^3+6xy^2+9x^2y-4y`
`=y(y^2+6xy+9x^2)-4y`
`=y(y+3x)^2-4y`
`=y[(y+3x)^2-4]`
`=y(y+3x-2)(y+3x+2)`
________________________________________
`b)3x+3y-x^2-y^2-2xy`
`=3(x+y)-(x+y)^2`
`=(x+y)(3-x-y)`
________________________________________
`c)x^2+5x-6`
`=x^2+6x-x-6`
`=x(x+6)-(x+6)=(x+6)(x-1)`
________________________________________
`d)2x^2+9x+9`
`=2x^2+6x+3x+9`
`=2x(x+3)+3(x+3)=(x+3)(2x+3)`
________________________________________
`e)x^2+3x-10`
`=x^2+5x-2x-10`
`=x(x+5)-2(x+5)=(x+5)(x-2)`
\(Bài2\\ a,x\left(4x^2-49\right)=0\\ \left[{}\begin{matrix}x=0\\4x^2-49=0\end{matrix}\right.=>\left[{}\begin{matrix}x=0\\4x^2=49\end{matrix}\right.\\ =>\left[{}\begin{matrix}x=0\\x^2=\dfrac{49}{4}\end{matrix}\right.=>x=0;x=\dfrac{7}{2};x=-\dfrac{7}{2}\\ b,9x^2\left(x+3\right)-4\left(3+x\right)=0\\ \left(9x^4-4\right)\left(3+x\right)=0\\ \left(3x-2\right)\left(3x+2\right)\left(x+3\right)=0\\ \left[{}\begin{matrix}x+3=0\\3x-2=0\\3x+2=0\end{matrix}\right.=>x=-3;x=\dfrac{2}{3};x=-\dfrac{2}{3}\)
\(c,\left(3x-2-2x-3\right)\left(3x-2+2x+3\right)=0\\ \left(x-5\right)\left(5x+1\right)=0\\ \left[{}\begin{matrix}x-5=0\\5x+1=0\end{matrix}\right.=>x=5;x=-\dfrac{1}{5}\\ d,2x\left(x-5\right)-\left(x-5\right)=0\\ \left(2x-1\right)\left(x-5\right)=0\\ \left[{}\begin{matrix}2x-1=0\\x-5=0\end{matrix}\right.=>x=\dfrac{1}{2};x=5\)
