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\(x^6-9x^5+30x^4-45x^3+30x^2-9x+1\)
\(=\left(x^2\right)^3-9x^5+30x^4-45x^3+30x^2-9x+1^3\)
\(=\left(x^3-3x+1\right)^3\)
\(x^2-3\)
\(=x^2-\left(\sqrt{3}\right)^2\)
\(=\left(x-\sqrt{3}\right)\left(x+\sqrt{3}\right)\)
\(\text{a) }x^4+64\)
\(=x^4+16x^2+64-16x^2\)
\(=\left(x^4+16x^2+64\right)-16x^2\)
\(=\left(x^2+8\right)^2-\left(4x\right)^2\)
\(=\left(x^2+4x+8\right)\left(x^2-4x+8\right)\)
\(\text{b) }4x^4+81y^4\)
\(=4x^4+36x^2y^2+81y^4-36x^2y^2\)
\(=\left(4y^4+36x^2y^2+81y^4\right)-36x^2y^2\)
\(=\left(2x^2+9y^2\right)^2-\left(6xy\right)^2\)
\(=\left(2x^2+9y^2+6xy\right)\left(2x^2+9y^2-6xy\right)\)
a. x4 + 64
= (x2)2 + 2x28 + 82 - 2x28
= (x2 + 8)2 - (4x)2
= (x2 + 8 + 4x)(x2 + 8 - 4x)
b. 4x4 + 81y4
= (2x2)2 + (9y2)2
Làm tới đây bí rồi bạn! Mà hình như làm gì có công thức a2 + b2
\(4a^4+81=\left(2a^2\right)^2+2\cdot9^2\cdot2a^2+9^4-2\cdot9^2\cdot2a^2\)
\(=\left(2a^2+9^2\right)^2-\left(18a\right)^2=\left(2a^2+9^2+18a\right)\left(2a^2+9^2-18a\right)\)
\(x^3\left(x^2-7\right)^2-36x\)
\(=x.\left[x^2.\left(x^2-7\right)^2-36\right]\)
\(=x.\left[\left(x^3-7x\right)^2-6^2\right]\)
\(=x.\left(x^3-7x-6\right).\left(x^3-7x+6\right)\)
\(=x.\left(x+1\right)\left(x^2-x-6\right).\left(x-1\right).\left(x^2+x-6\right)\)
\(=x.\left(x+1\right).\left(x+2\right).\left(x+3\right).\left(x-1\right).\left(x-2\right).\left(x-3\right)\)
Ta có : \(x^3\left(x^2-7\right)^2-36x\)
= \(x^3\left(x^4-14x^2+49\right)-36x\)
= \(x\left(x^6-14x^4+49x^2-36\right)\)
= \(x\left(x^2-1\right)\left(x^2-4\right)\left(x^2-9\right)\)---- chỗ này tắt
= (x-3)(x-2)(x-1)x(x+1)(x+2)(x+3)
x4 + 4
= x4 + 4 + 4x² - 4x² = ( x² + 2 )² - 4x²
= ( x² + 2 - 2x )( x² + 2 + 2x )
P/s: Giang Lê Trà My lần sau giải cho cẩn thận vào nhé.
\(64x^4+y^4\)
\(=\left(64x^4+16x^2y^2+y^4\right)-16x^2y^2\)
\(=\left(8x^2+y^2\right)^2-16x^2y^2\)
\(=\left(8x^2+y^2-4xy\right)\left(8x^2+y^2+4xy\right)\)
\(x^5+x-1\)
\(=x^5+x^2-\left(x^2-x+1\right)\)
\(=x^2\left(x^3+1\right)-\left(x^2-x+1\right)\)
\(=x^2\left(x+1\right)\left(x^2-x+1\right)-\left(x^2-x+1\right)\)
\(=\left(x^2-x+1\right)\left(x^3+x^2-1\right)\)
x4 - 30x2 + 31x - 30
= x4 + x - 30x2 + 30x - 30
= x(x3 + 1) - 30(x2 - x + 1)
= x(x + 1)(x2 - x + 1) - 30(x2 - x + 1)
= (x2 - x + 1)[x(x + 1) - 30]
= (x2 - x + 1)(x2 + x - 30)
= (x2 - x + 1)(x2 - 5x + 6x - 30)
= (x2 - x + 1)[x(x - 5) + 6(x - 5)]
= (x2 - x + 1)(x - 5)(x + 6)
opps, thank very much