Áp dụng hằng đẳng thức `a^2+-2ab+b^2`
a)
`(x+1)^2+2(x+1)+1=(x+1+1)^2=(x+2)^2`
b)
`(y-1)^2+2(y-1)+1=(y-1+1)^2=y^2`
c)
`(z+2)^2+4(z+2)+4=(z+2+2)^2=(z+4)^2`
d)
`(a-3)^2-6(a-3)+9=(a-3-3)^2=(a-6)^2`
e)
`(b^2+5)^2-10(b^2+5)+25=(b^2+5-5)^2=(b^2)^2=b^4`
f)
`(2x+3)^2-4x(2x+3)+4x^2=(2x+3-2x)^2=3^2=9`
g)
`(x+y)^2-2y(x+y)+y^2=(x+y-y)^2=x^2`
h)
`(2x+3)^2+2(2x+3)(x-3)+(x-3)^2=(2x+3+x-3)^2=(3x)^2=9x^2`
i)
`(x+1)^2+2(x+1)(x-1)+(x-1)^2=(x+1+x-1)^2=x^2`
j)
`(3x+5)^2-2(3x+5)(2x-5)+(2x-5)^2=[3x+5-(2x-5)]^2=(x+10)^2`
k)
`(x+y+1)^2-2(x+y+1)(x+y)+(x+y)^2=[x+y+1-(x+y)]^2=1^2=1`
l)
`(a+b-c)^2+2(a+b-c)(c-b)+(b-c)^2=(a+b-c)^2-2(a+b-c)(b-c)+(b-c)^2=[a+b-c-(b-c)]^2=a^2`
m)
`(3x-5z)^2+2(4z-3x)(3x-5z)+(4z-3x)^2=(3x-5z+4z-3x)^2=(-z)^2=z^2`
n)
`(x^2+2x+2)^2-2(x^2+2x+2)+1=(x^2+2x+2-1)^2=(x^2+2x+1)^2=[(x+1)^2]^2=(x+1)^4`
