3a)

\(A=x^3-9x^2+27x-27\)

\(=\left(x-3\right)^3=\left(1-3\right)^3=-8\)

1a) \(36a^4-y^2\)

\(=\left(6a^2\right)^2-y^2\)

\(=\left(6a^2+y\right)\left(6a^2-y\right)\)

4x² - 6x

= 2x . (2x - 3)

Trả lời:

a, \(\left(xy+4\right)^2-4\left(x+y\right)^2\)

\(=\left(xy+4\right)^2-\left[2\left(x+y\right)\right]^2\)

\(=\left(xy+4\right)^2-\left(2x+2y\right)^2\)

\(=\left(xy+4-2x-2y\right)\left(xy+4+2x+2y\right)\)

\(=\left[\left(xy-2x\right)-\left(2y-4\right)\right]\left[\left(xy+2x\right)+\left(2y+4\right)\right]\)

\(=\left[x\left(y-2\right)-2\left(y-2\right)\right]\left[x\left(y+2\right)+2\left(y+2\right)\right]\)

\(=\left(y-2\right)\left(x-2\right)\left(y+2\right)\left(x+2\right)\)

b, \(2x-\sqrt{x}=2.\sqrt{x}.\sqrt{x}-\sqrt{x}=\sqrt{x}.\left(2\sqrt{x}-1\right)\)

Ta chứng minh C chia hết cho 11 và 17 vì 11 và 17 nguyên tố cùng nhau

C chia hết cho 11 vì \(C=\left(16^n-5^n\right)+\left(12^n-1^n\right)⋮11+11⋮11\)

C chia hết cho 17 vì \(C=\left(16^n-1^n\right)+\left(12^n-5^n\right)⋮17+17⋮17\)

Ta có đpcm

cảm ơn bạn nha

a) 4x³-64x=4x.(x²-4²)=4x.(x-4).(x+4)

b)x³-27+(3-x).(9-4x)=x³-27+27-12x-9x+4x²=x³-21x+4x²=x.(x²-21+4x)