Bài 4:
a)
`x^2+2x+1=(x+1)^2`
b)
`x^2-8x+16=x^2-2.x.4+4^2=(x-4)^2`
c)
`(x^2)/4+x+1=1/4x^2+x+1=(1/2x)^2+2. 1/2x . 1+1^2=(1/2x+1)^2`
d)
`4x^2-8xy+4y^2=(2x)^2-2.2x.2y+(2y)^2=(2x-2y)^2`
Bài 5:
a)
`4x^2+4x+1=(2x)^2+2.2x.1+1^2=(2x+1)^2`
b)
`9x^2-12x+4=(3x)^2-2.3x.2+2^2=(3x-2)^2`
c)
`1/4a^2b^4+ab^2+1=(1/2ab^2)^2+2. 1/2ab^2 . 1 +1^2=(1/2ab^2+1)^2`
d)
`16u^2v^4-8uv^2+1=(4uv^2)^2-2.4uv^2 . 1+1^2=(4uv^2-1)^2`
Áp dụng:
`(a-b)^2=a^2-2ab+b^2`
`(a+b)^2=a^2+2ab+b^2`.
