Bài 3:
a) \(25x^2-\dfrac{1}{4}\)
\(=\left(5x\right)^2-\left(\dfrac{1}{2}\right)^2\)
\(=\left(5x-\dfrac{1}{2}\right)\left(5x+\dfrac{1}{2}\right)\)
b) \(36x^2+12xy+y^2\)
\(=\left(6x\right)^2+2\cdot6x\cdot y+y^2\)
\(=\left(6x+y\right)^2\)
c) \(\dfrac{x^3}{2}+4\)
\(=\dfrac{1}{2}\left(x^3+8\right)\)
\(=\dfrac{1}{2}\left(x^3+2^3\right)\)
\(=\dfrac{1}{2}\left(x+2\right)\left(x^2-2x+4\right)\)
d) \(27y^3+27y^2+9y+1\)
\(=\left(3y\right)^3+3\cdot\left(3y\right)^2\cdot1+3\cdot3y\cdot1+1^3\)
\(=\left(3y+1\right)^3\)
ai làm nốt b1;2;4;5;6 giúp mik vs ạ . mai mới hết hạn a.mik nhớ nhầm lịch
