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2(x2 + y2)(x + y)2 ? (x2 ? y2)2 (3a + b)(3a ? b) ? (a + 5b)(b ? 3a) (x2 + y2)2 ? 4x2y2 4(2x ? y)(3x ? y) ? 4(y ? 2x)(x + 3y) ? 49m3yz3 + 14x2y2z2 ? 21my3z m(ab + bc + ac) ? mbc p2(p + q)2 ? q2(p ? q)2 唔該!

最佳解答:

1. 2(x^2 + y^2)(x + y)^2 ? (x^2 ? y^2)^2 = 2(x^2 + y^2)(x + y)^2 ? [(x+y)(x? y)]^2 = 2(x^2 + y^2)(x + y)^2 ? (x+y)^2(x? y)^2 = (x+y)^2 [2(x^2 + y^2)? (x? y)^2 ] = (x+y)^2 [2x^2 + 2y^2? (x^2? 2xy +y^2) ] = (x+y)^2 [x^2 + 2xy +y^2 ] = (x+y)^2 [(x+y)^2] = (x+y)^4 2. (3a + b)(3a ? b) ? (a + 5b)(b ? 3a) = (3a + b)(3a ? b) + (a + 5b)(3a - b) = (3a - b) [(3a + b) + (a + 5b)] = (3a-b)(4a+6b) = 2(3a-b)(2a+3b) 3. (x2 + y2)^2 ? 4x^2 y^2 = x^4 + 2x^2 y^2 + y^4 - 4x^2 y^2 = x^4 - 2x^2 y^2 + y^4 = (x^2 - y^2) ^2 4. 4(2x ? y)(3x ? y) ? 4(y ? 2x)(x + 3y) = 4(2x ? y)(3x ? y) + 4(2x ? y)(x + 3y) = 4(2x-y) [(3x-y)+(x+3y)] = 4(2x-y)(4x+2y) = 8(2x-y)(2x+y) 5. ? 49m3yz3 + 14x2y2z2 ? 21my3z = (-7)myz(7m^2z^2 - 2myz +3 y^2) 6. m(ab + bc + ac) ? mbc = m(ab+bc+ac-bc) =m(ab+ac) =ma(b+c) 7. p2(p + q)2 ? q2(p ? q)2 = p^2[p^2+2pq+q^2] - q^2 [p^2-2pq+q^2] = p^4 +2p^3q + p^2 q^2 - p^2 q^2 +2pq^3 - q^4 = p^4 +2p^3q +2pq^3 - q^4 = p^4 - q^4 +2p^3q +2pq^3 = (p^2 + q^2)(p^2 - q^2) + 2pq (q^2+p^2) = (p^2 + q^2) ( p^2 - q^2 + 2pq)

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