`1)`
`a)81^2`
`=(80+1)^2`
`=80^2+2.80.1+1^2`
`=6400+160+1`
`=6561.`
`b)102^2`
`=(100+2)^2`
`=100^2+2.100.2+2^2`
`=10000+400+4`
`=10404.`
`c) 97.103`
`=(100-3)(100+3)`
`=100^2-3^2`
`=10000-9`
`=9991.`
`d) 249.351`
`=(300-51).(300+51)`
`=300^2-51^2`
`=90000-2601`
`=87399.`
`2)`
`a)16x^2+24x+9`
`=(4x)^2+2.4x.3+3^2`
`=(4x+3)^2.`
`b)x^2/4-3x+9`
`=(x/2)^2-2.x/2.3 + 3^2`
`=(x/2-3)^2.`
`c)4u^4v^8+(u^2v^4)^4+4`
`=[(u^2v^4)^2]^2+2.u^4v^8+2^2.`
`=(u^4v^8)^2+2.u^4v^8+2^2.`
`=(u^4v^8+2)^2.`
`d) 25/v^2-10/v+1`
`=(5/v)^2-2. 5/v.1+1^2`
`=(5/v-1)^2.`
`e)(-m+2n)^2+2.(2n-m)+1`
`=(2n-m)^2+2.(2n-m).1+1^2`
`=(2n-m+1)^2.`
`f) (2p-4q)^2+4p-8p+1`
`= (2p-4q)^2+2.(2p-4p).1+1^2`
`=(2p-4q+1)^2.`
Sửa lại đề phần `c), e)` nhé.
