好多條難數!!!help!!!

I think that you typed Q3 wrong.

2010-10-08 22:31:06 補充：
(2a-3b)(?)=8a^3-27b^3
8a^3-27b^3=(2a-3b)(4a^2+6ab+9b^2)

(?)=2a-3b)(4a^2+6ab+9b^2)/(2a-3b)
(?)=4a^2+6ab+9b^2
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.(?)(x^2+xy^2+y^4)=x^3-y^6

x^3-y^6=(x-y^2)(x^2+xy^2+6)

.(?)(x^2+xy^2+y^4)=(x-y^2)(x^2+xy^2+6)

(?)=x-y^2
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If (a-b)^2=m and (a+b)^2=n,express(a-b)^3(a=b)^5(b^2-a^2) in terms of m and n(Unreadable)
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a-b=1 and ab=2,find the value of a^2+b^2
(a-b)^2=1^2
a^2-2ab+b^2=1
a^2+b^2=5
________________
5.If a+b+c=5 and ab+bc+ac=3,find the value of a^2+b^2+c^2
( (a+b)+c)^2=5 ^2
(a+b)^2+2c(a+b)+c^2
a^2+2ab+b^2+2ac+2bc+c^2
a^2+b^2+c^2+2(ab+ac+bc)
__________
a^2+b^2+c^2+2(ab+ac+bc)=6
a^2+b^2+c^2+6=6
a^2+b^2+c^2=0
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6.If x-y=14 and x^3-y^3=42,find the value of x^2+xy+y^2

x^3-y^3=42=(x-y)(x^2+xy+y^2)
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(x-y)(x^2+xy+y^2)=42
x^2+xy+y^2=3
______________________
((2x+3y)(3y-2x)/(2x-3y))^2(6y-4x)^2
(-(2x+3y)(2x-3y)/(2x-3y))^2(6y-4x)^2
(2x+3y)^2(6y-4x)^2
(2x+3y)^2(4x-6y)^2
4(2x+3y)^2(2x-3y)^2
4(2x+3y)(2x-3y)(2x-3y)(2x+3y)
4(4x^2-9y^2)(4x^2-9y^2)
4(16x^4-72x^2y^2+81y^4)
64x^4+288x^2y^2+324y^4




2010-10-08 22:38:29 補充：
64x^4-288x^2y^2+324y^4

2010-10-08 22:39:48 補充：
All of the questions are not very difficult,but you must think them

2010-10-09 00:24:45 補充：
.If a+b+c=5 and ab+bc+ac=3,find the value of a^2+b^2+c^2
( (a+b)+c)^2=5 ^2
(a+b)^2+2c(a+b)+c^2=25
a^2+2ab+b^2+2ac+2bc+c^2=25
a^2+b^2+c^2+2(ab+ac+bc)=25
__________
a^2+b^2+c^2+2(ab+ac+bc)=25
a^2+b^2+c^2+6=25
a^2+b^2+c^2=19

第三條真系敢寫,但都要唔該你