bạn áp dụng các hằng đẳng thức là Ok:
a) \(-4x^2+12xy-9y^2+25=-\left(2x\right)^2+2.2x.3y-\left(3y\right)^2+25\)
= \(-\left(2x-3y\right)^2+25=\left(5-2x+3y\right)\left(5+2x-3y\right)\)
b) \(x^3-3x^2+3x-1=\left(x^3-1\right)-\left(3x^2-3x\right)=\left(x-1\right)\left(x^2+x+1^2\right)-3x\left(x-1\right)\)
= \(\left(x-1\right)\left(x^2+x+1^2-3x\right)=\left(x-1\right)\left(x^2-2x+1\right)=\left(x-1\right)\left(x-1\right)^2=\left(x-1\right)^3\)
c) \(a^6-a^4+2a^3+2a^2=a^2\left(a^4-a^2+2a+2\right)=a^2\left[a^2\left(a^2-1\right)+2\left(a+1\right)\right]\)
= \(a^2\left[a^2\left(a+1\right)\left(a-1\right)+2\left(a+1\right)\right]=a^2\left(a+1\right)\left(a^3+a^2+2\right)\)