maths

第1條有無有打錯問題?

2010-11-06 11:24:49 補充：
1. (-2a^4)b^4+32c^4
=-2[(a^4)b^4-16c^4]
=-2(a^2*b^2+4c^2)(a^2*b^2-4c^2)
=-2(a^2*b^2+4c^2)(ab-2c)(ab+2c)

2. x^2+y^2=58,xy=21,(x+y)^2 and(x-y)^2=?and?
(x+y)^2
=x^2+2xy+y^2
=x^2+y^2+2xy
=58+2(21)
=58+42
=100

(x-y)^2
=x^-2xy+y^2
=x^2+y^2-2xy
=58-2(21)
=58-42
=16


2010-11-06 13:16:15 補充：
第3條匿名已答了

3.3(x^2-1)+Ax+15=(B-x)(Cx-2)
findA,B,C
3x^2 + Ax + 12 = -Cx^2 + (BC+2)x - 2B
-C = 3, C = -3,
-2B = 12, B = -6
BC+2 = A, 18+2 = A, A = 20

2a^4b^4+32c^4
2(16c^4-a^4b^4)
2((4c^2)^2-(a^2b^2)^2)
2(4c^2-a^2b^2)(4c^2+a^2b^2)
2(2c-ab)(2c+ab)(4c^2+a^2b^2)

2010-11-06 12:05:44 補充：
x^2+y^2=58,xy=21,(x+y)^2 and(x-y)^2=?and?

(x+y)^2
x^2+2xy+y^2
=100

(x-y)^2
x^2-2xy+y^2
=16

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