x2 + 4x –y2 + 4
= (x2 +4x + 4) – y2
= (x +2)2 – y2
= ( x + 2 + y)(x + 2 –y)
\(x^2+4x-y^2+4=\left(x^2+4x+4\right)-y^2=\left(x+2\right)^2-y^2=\left(x+2-y\right)\left(x+2+y\right)\)
x2 + 4x –y2 + 4
= (x2 +4x + 4) – y2
= (x +2)2 – y2
= ( x + 2 + y)(x + 2 –y)
\(x^2+4x+y^2+4\)
\(\text{Phân tích thành nhân tử }\)
\(\left(x+2+y\right)\left(x+2-y\right)\)
\(x^2+4x-y^2+4\)
\(=\left(x+2\right)^2-y^2\)
\(=\left(x-y+2\right)\left(x+y+2\right)\)
hk tốt
^^