Homework Help: maths

Posted by jenn on Tuesday, November 17, 2009 at 10:21am.

use the substitution method to solve the linear system.
1. 3x=9
-x+2y=9

3x/3 = 9/3
x = 3

-x(3)+2y = 9
-3+2y = 9
2y = 12
y = 6

is (3,6) correct?

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also, can you please tell me how to solve these?

use the linear combinations to solve the linear system:
2.x+y=3
x+2y=6

3. x+y=7
y=-2x+8

thanks

maths - bobpursley, Tuesday, November 17, 2009 at 11:06am
Yes, on (3.6)

2)
x+y=3
x+2y=6

subtract the second equation from the first:

x+y=3
-(x+2y=6)
or the result is -y=-3
y=3
then go back and solve for x.

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