Bài 1:
$a)(3-2y)^2_{}$
$⇔4y^2-12y+9_{}$
$b)(3x+5y)^3_{}$
$⇔(3x)^3+3.(3x)^2.5y+3.3x(5y)^2+(5y)^3_{}$
$⇔27x^3+3.9x^2.5y+3.3x.25y^2+125y^3_{}$
$⇔27x^3+135x^2y+225xy^2+125y^3_{}$
$+)Nếu_{}$ $(3x+5y)^2_{}$ $thì{}:$
$⇔(3x)^2+2.3x.5y+(5y)^2_{}$
$⇔9x^2+30xy+25y^2_{}$
$c)(6x-3y)^2_{}$
$⇔(6x)^2-2.6x.3y+(3y)^2_{}$
$⇔36x^2-36xy+9y^2_{}$
$d)(3x+y)^2_{}$
$⇔(3x)^2+2.3xy+y^2_{}$
$⇔9x^2+6xy+y^2_{}$
$e)(2x-1)^3_{}$
$⇔(2x)^3-3.(2x)^2.1+3.2x.1^2-1^3_{}$
$⇔8x^3-3.4x^2.1+3.2x.1-1_{}$
$⇔8x^3-12x^2+6x-1_{}$
$d)8x^3-y^3_{}$
$⇔2^3x^3-y^3_{}$
$⇔(2x)^3-y^3_{}$
$⇔(2x-y).[(2x)^2+2xy+y^2 ] _{}$
$⇔(2x-y)(4x^2+2xy+y^2)_{}$
