system of equations

unique · 2006-10-13 02:06:51

ok i know how to solve system of equations but with this one i am having problems !

1) a - b = 1
2) b - 2c = 1
3) 3a - 4c = 7

ok i know that
you have to first
1equation subtract 2equation
and then
2equation plus 3equation
i know that
but you see that in each equation one letter is missing
so how can we
subtract a-b=1 from b-2c=1
is we dont have a or c????

and same goes for the second part

help:/

unique · 2006-10-13 02:09:38

it cant be this way right?

a - b = 1
- b - 2c = 1 cross out the b's
------------------
a - 2c = 0 ????

pi man · 2006-10-13 02:16:07

Add the first 2 equations together:

Multiply both sides by -2 and then add it to the 3rd equation\\

unique · 2006-10-13 02:38:30

a = 3
so put in the value in the equation:
3a - 4c = 7
3(3) - 4c = 7
9 - 4c = 7
subtract 9 both sides
-4c = -2
divide
c = 0.5 or 1/2 right

then c = 0.5
put in value

b - 2c = 1
b - 2(0.5) = 1
b - 1 = 1
add 1 both sides
b = 2 correct

THANKS

Math Is Fun Forum

#1 2006-10-13 02:06:51

system of equations

#2 2006-10-13 02:09:38

Re: system of equations

#3 2006-10-13 02:16:07

Re: system of equations

#4 2006-10-13 02:38:30

Re: system of equations

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