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#1 2006-11-07 12:44:08
- Neha
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- Registered: 2006-10-11
- Posts: 173
systems
solve the system of equations by the substitution method:
a + 1/2b = 16
2a + b = 50
ok i know how to do equations such as these but this has a fraction......so help
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#2 2006-11-07 15:37:52
- pi man
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- Registered: 2006-07-06
- Posts: 251
Re: systems
Multiply both sides of the 1st equation by 2:
Now subtract your new first equation from your second:
Multiply both sides by b:
You can use the quadratic formula to solve this now.
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#3 2006-11-08 04:38:51
- Neha
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- Registered: 2006-10-11
- Posts: 173
Re: systems
ok thanks
i haev do the quadratic formula....
and stoped here
x = 18 +- sqrt(-320) / 2
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#4 2006-11-09 02:07:54
- Neha
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- Registered: 2006-10-11
- Posts: 173
Re: systems
hello guys what to do next......
18 +- sqrt(-320)
x = -------------------
2
help
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#5 2006-11-11 08:09:36
- Neha
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- Registered: 2006-10-11
- Posts: 173
Re: systems
I THINK YOU WRONG
a+1/2b=16
2a+b=50
2a=50-b
a=(50-b)/2
substituting in eqn. 1
(50-b)/2+1/2b=16
multiplying by 2b
b(50-b)+1=32b
50b-b^2+1-32b=0
-b^2+18b+1=0
=>b^2-18b-1=0
b=[18+/-rt(324+4)]/2
=[9+/-rt82]
similarly express b interms of a and find a
or substitute the value of a
i have a feeling your sum might be
a+(1/2)*b=16
and 2a+b=50
these are the equations of parallel lines
and hence no solution
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#6 2006-11-11 13:40:13
- krassi_holmz
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- Registered: 2005-12-02
- Posts: 1,905
Re: systems
b!=0
Last edited by krassi_holmz (2006-11-11 13:47:43)
IPBLE: Increasing Performance By Lowering Expectations.
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#7 2006-11-11 13:53:52
- Ricky
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- Registered: 2005-12-04
- Posts: 3,791
Re: systems
a + 1/2b = 16
2a + b = 50
Twice it was assumed that it is 1/(2b) in the first equation, where as I'm pretty sure it is in fact (1/2)b.
Normally students are asked to solve systems of linear equations.
"In the real world, this would be a problem. But in mathematics, we can just define a place where this problem doesn't exist. So we'll go ahead and do that now..."
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#8 2006-11-11 13:59:20
- krassi_holmz
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- Registered: 2005-12-02
- Posts: 1,905
Re: systems
If it's (1/2)b:
No solution.
IPBLE: Increasing Performance By Lowering Expectations.
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