Đáp án:
a/ `(x/3+4y)^2`
`= (x/3)^2+2.(x/3).4y+(4y)^2`
`= (x^2)/9+(8xy)/3+16y^2`
b/ `(1/x-3/y)^2`
`= (1/x)^2-2. 1/x . 3/y+(3/y)^2`
`= 1/(x^2)-6/(xy)+9/(y^2)`
c/ `(3x-4y)^2`
`= (3x)^2-2.3x.4y+(4y)^2`
`= 9x^2-24xy+16y^2`
d/ `(3x+5/2y)^2`
`= (3x)^2+2.3x . 5/2y+(5/2y)^2`
`= 9x^2+15xy+(25y^2)/4`
e/ `(x/2-2y)^2`
`= (x/2)^2-2. x/2. 2y+(2y)^2`
`= (x^2)/4-2xy+4y^2`
f/ `(x-2y-3)^2`
`= x^2+(2y)^2+3^2-4xy-6x+12y`
`= x^2+4y^2+9-4xy-6x+12y`
