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250x4+54x=2x(125x3+27)
=2x[(5x)3+33]]
=2x(5x+3)[(5x)2-(5x)*3+32]
=2x(5x+3)(25x2-15x+9)
\(54x^3+16y^3\)
\(=2\left(27x^3+8y^3\right)\)
\(=2\left[\left(3x\right)^3+\left(2y\right)^3\right]\)
\(=2\left(3x+2y\right)\left(9x^2-6xy+4y^2\right)\)
\(x^4-16y^4\)
\(=\left(x^2\right)^2-\left(4y^2\right)^2\)
\(=\left(x^2-4y^2\right)\left(x^2+4y^2\right)\)
\(=\left(x-2y\right)\left(x+2y\right)\left(x^2+4y^2\right)\)
Chúc bạn học tốt.
\(54x^3+16y^3=2\left(27x^3+8y^3\right)\)
\(=2\left[\left(3x\right)^3+\left(2y\right)^3\right]\)
\(=2\left(3x+2y\right)\left[\left(3x\right)^2-3x.2y+\left(2y\right)^2\right]\)
\(=2\left(3x+2y\right)\left(9x^2-6xy+4y^2\right)\)
Đặt \(A=\left(x-2\right)\left(x-4\right)\left(x-5\right)\left(x-10\right)-54x^2\)
\(=\left[\left(x-2\right)\left(x-10\right)\right]\left[\left(x-4\right)\left(x-5\right)\right]-54x^2\)
\(=\left(x^2-12x+20\right)\left(x^2-9x+20\right)-54x^2\)
Đặt \(x^2-12x+20=t\)
Khi đó: \(A=t\left(t+3x\right)-54x^2\)
\(=t^2+3tx-54x^2\)
\(=t\left(t-6x\right)+9x\left(t-6x\right)\)
\(=\left(t-6x\right)\left(t+9x\right)\)
\(=\left(x^2-18x+20\right)\left(x^2-3x+20\right)\)
\(A=x^4-6x^3+27x^2-54x+32\)
\(=x^4-5x^3+22x^2-32x-x^3+5x^2-22x+32\)
\(=x\left(x^3-5x^2+22x-32\right)-\left(x^3-5x^2+22x-32\right)\)
\(=\left(x-1\right)\left(x^3-5x^2+22x-32\right)\)
\(=\left(x-1\right)\left(x^3-3x^2+16x-2x^2+6x-32\right)\)
\(=\left(x-1\right)\left[x\left(x^2-3x+16\right)-2\left(x^2-3x+16\right)\right]\)
\(=\left(x-1\right)\left(x-2\right)\left(x^2-3x+16\right)\)
Vì \(x\in Z\)=> x-1;x-2 là 2 số nguyên liên tiếp => \(\left(x-1\right)\left(x-2\right)⋮2\)
\(\Rightarrow A=\left(x-1\right)\left(x-2\right)\left(x^2-3x+16\right)⋮2\) hay A là số chẵn (đpcm)
\(A=x^4-6x^3+27x^2-54x+32\)
\(=x^4-x^3-5x^3+5x^2+22x^2-22x-32x+32\)
\(=\left(x-1\right)\left(x^3-5x^2+22x-32\right)\)
\(=\left(x-1\right)\left[x^2\left(x-2\right)-3x\left(x-2\right)+16\left(x-2\right)\right]\)
\(=\left(x-1\right)\left(x-2\right)\left(x^2-3x+16\right)\)
Vì \(\left(x-1\right)\left(x-2\right)⋮2\) nên A là số chẵn với mọi x thuộc Z
1) 3-81x3
=3-3.(3x)3
=3[13-(3x)3)]
=3(1-3x)(1+3x+9x2)
2) 250x3y3-2
=2(125x3y3-1)
=2[(5xy)3-13]
=2(5xy-1)(25x2y2+5xy+1)
3) a4+4b4
=[(a2)2+4a2b2+(2b2)]-4a2b2
=(a2+2b2)-(2ab)2
=(a2+2b2-2ab)(a2+2b2+2ab)
4) x5+x+1
=x5-x2+x2+x+1
=x2(x3-13)+(x2+x+1)
=x2(x-1)(x2+x+1)+(x2+x+1)
=(x2+x+1)[x2(x-1)+1]
=(x2+x+1)(x3-x2+1)
Chúc bn học giỏi nhoa!!!
a)x^2+2x-4y^2-4y
=(x2-4y2)+(2x-4y)
=(x-2y)(x+2y)+2.(x-2y)
=(x-2y)(x+2y+2)
b)x^4-6x^3+54x-81
=(x4-81)+(-6x3+54x)
=(x2-9)(x2+9)-6x.(x2-9)
=(x2-9)(x2+9-6x)
=(x-3)(x+3)(x-3)2
=(x-3)3(x+3)
c)ax^2+ax-bx^2-bx-a+b
=(ax2-bx2)+(ax-bx)+(-a+b)
=x2.(a-b)+x.(a-b)-(a-b)
=(a-b)(x2+x+1)
\(x^2-y^2+4x+4\)
\(=\left(x+2\right)^2-y^2\)
\(=\left(x+2+y\right)\left(x+2-y\right)\)
\(4x^2-y^2+8\left(y-2\right)\)
\(=4x^2-\left(y^2-8y+16\right)\)
\(=4x^2-\left(y-4\right)^2\)
\(=\left(2x+y-4\right)\left(2x-y+4\right)\)