a: \(x^3+x^2+x+1\)
\(=\left(x^3+x^2\right)+\left(x+1\right)\)
\(=x^2\left(x+1\right)+\left(x+1\right)\)
\(=\left(x+1\right)\left(x^2+1\right)\)
b: Sửa đề: \(ax+ay-3x-3y\)
\(=\left(ax+ay\right)-\left(3x+3y\right)\)
\(=a\left(x+y\right)-3\left(x+y\right)\)
\(=\left(x+y\right)\left(a-3\right)\)
c: \(x^2+ab+ax+bx\)
\(=\left(x^2+ax\right)+\left(ab+bx\right)\)
\(=x\left(x+a\right)+b\left(a+x\right)\)
\(=\left(x+a\right)\left(x+b\right)\)
d: \(xy+1+x+y\)
\(=\left(xy+x\right)+\left(y+1\right)\)
\(=x\left(y+1\right)+\left(y+1\right)\)
\(=\left(x+1\right)\left(y+1\right)\)
a.
\(x^3+x^2+x+1\\ =x^2\left(x+1\right)+\left(x+1\right)\\ =\left(x^2+1\right)\left(x+1\right)\)
b.
\(ax+ay-3x-3y\\ =ax+ay-\left(3x+3y\right)\\ =a\left(x+y\right)-3\left(x+y\right)\\ =\left(a-3\right)\left(x+y\right)\)
c.
\(x^2+ab+ax+bx\\ =\left(x^2+ax\right)+\left(ab+bx\right)\\ =x\left(x+a\right)+b\left(a+x\right)\\ =\left(x+a\right)\left(x+b\right)\)
d.
\(xy+1+x+y\\ =\left(xy+x\right)+\left(1+y\right)\\ =x\left(y+1\right)+\left(y+1\right)\\ =\left(x+1\right)\left(y+1\right)\)
b.
ax+ay−3x−3y=ax+ay−(3x+3y)=a(x+y)−3(x+y)=(a−3)(x+y)
d.
xy+1+x+y=(xy+x)+(1+y)=x(y+1)+(y+1)=(x+1)(y+1)