Đáp án_Giải thích các bước giải:
`a)` `(x+3)^2=x^2+2*x*3+3^2=x^2+6x+9`
`b)` `(y-5)^2=y^2-2*y*5+5^2=y^2-10y+25`
`c)` `4x^2-16y^2`
`=(2x)^2-(4y)^2`
`=(2x-4y)(2x+4y)`
`=2x*2x+2x*4y-4y*2x-4y*4y`
`=4x^2+8xy-8xy-16y^2`
`=4x^2-16y^2`
`d)` `(2x+5y)^2=(2x)^2+2*2x*5y+(5y)^2=4x^2+20xy+25y^2`
`e)` `(4x-3y)^2=(4x)^2-2*4x*3y+(3y)^2=16x^2-24xy+9y^2`
`f)` `9x^2-25y^2`
`=(3x)^2-(5y)^2`
`=(3x-5y)(3x+5y)`
`=3x*3x+3x*5y-5y*3x-5y*5y`
`=9x^2+15xy-15xy-25y^2`
`=9x^2-25y^2`
`g)` `(1/4x+4/3y)^2`
`=(1/4x)^2+2*1/4x*4/3y+(4/3y)^2`
`=1/16x^2+2/3xy+16/9y^2`
`h)` `(5/4y-1/5x)^2`
`=(5/4y)^2-2*5/4y*1/5x+(1/5x)^2`
`=25/16y^2-1/2xy+1/25x^2`
`i)` `x^4-y^4`
`=x^4+x^3y+x^2y^2+xy^3-x^3y-x^2y^2-xy^3-y^4`
`=x^4+x^3y+x^2y^2+xy^3-(x^3y+x^2y^2+xy^3+y^4)`
`=x(x^3+x^2y+xy^2+y^3)-y(x^3+x^2y+xy^2+y^3)`
`=(x-y)(x^3+x^2y+xy^2+y^3)`
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