f.2 maths

1.The error係0.1/2=0.05
so,percentage error =(0.05/1.2)*100%
=2.5%
2.(4b/3b+3)/(6b/ab+a)
=(4/3+3)/(6/a+a)
=(31/3)/(6a/a*a)
=(31/3)*(a*a/6a)
=(31a*a)/(18a)
=(31a/18)
3.n係個項數
so2到50既even number有25個
S=25(25+1)
=650
4.用cross method
抽3出來先
3(x^2 - 8x + 16)
=3(x-4)^2(a-b)^2個條equation
5.用cross method
5p^2 + 22p - 48
=(5p-8)(p+6)
6.用cross method
y(3x-y) - 3y^2 + x^2
=3xy-y^2-3y^2+x^2
=x^2+3xy-4y^2
=(x-y)(x+4y)
7.應該用(a-b)^2
依條唔識sorry!
希望help到you!

2006-12-28 23:09:15 補充：
1係4.17orr to 3 sig.fig)

2006-12-28 23:10:02 補充：
2.(4b/3b 3)/(6b/ab a)=(4/3 3)/(6/a a)=(13/3) / [(6 a^2)/a]=(13/3)* [a/ (6 a^2) ]=13a / (18 3 a^2)

2006-12-28 23:11:33 補充：
7.a^6 m^3 - b^3 n^3=(a^2 m)^3 - (bn)^3=(a^2 m -bn) ( a^4 m^2 a^2 b m n b^2 n^2)p.s.a^3 -b^3=(a-b)(a^2 ab b^2)a^3 b^3=(a b)(a^2 - ab b^2)

1.
percentage error =0.05/1.2*100%
=4.17% (2 d.p.)

2.(4b/3b+3)/(6b/ab+a)
=(4/3+3)/(6/a+a)
=(13/3) / [(6+a^2)/a]
=(13/3)* [a/ (6+a^2) ]
=13a / (18+3 a^2)

3.
2+4+6+...+50
=25(25+1)
=650

4.
3x^2 - 24x + 48
=3(x^2 - 8x + 16)
=3(x-4)^2

5.
5p^2 + 22p - 48
=(5p-8)(p+6)

6.
y(3x-y) - 3y^2 + x^2
=3xy-y^2-3y^2+x^2
=x^2+3xy-4y^2
=(x-y)(x+4y)

7.
a^6 m^3 - b^3 n^3
=(a^2 m)^3 - (bn)^3
=(a^2 m -bn) ( a^4 m^2 + a^2 b m n + b^2 n^2)

p.s.
a^3 -b^3
=(a-b)(a^2 + ab + b^2)

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