ATAR Notes: Forum

VCE Stuff => VCE Mathematics => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Mathematical Methods CAS => Topic started by: jag on January 30, 2009, 05:49:09 pm

Title: Methods help!
Post by: jag on January 30, 2009, 05:49:09 pm: 3s - ah = a^2
as+2h = 3a

write s in terms of a only
Title: Re: Methods help!
Post by: Flaming_Arrow on January 30, 2009, 05:55:26 pm: $3s - ah = a^2$

$as+2h = 3a$

$\frac{3s-a^2}{a} = h$

$as+2(\frac{3s-a^2}{a})= 3a$

$as+\frac{6s-2a^2}{a}=3a$

$a^2s+6s-2a^2=3a^2$

$a^2s+6s=5a^2$

$s(a^2+6)=5a^2$

$s = \frac{5a^2}{a^2+6}$
Title: Re: Methods help!
Post by: Mao on January 31, 2009, 12:05:40 am: alternative method:

[1] * 2: $6s-2ah=2a^2$ -- [3]
[2] * a: $a^2s + 2ah = 3a^2$ -- [4]

[3] + [4]: $(a^2+6)s = 5a^2\implies s=\frac{5a^2}{a^2+6}$