Question

Ok guys, easy one!

Solve this system using systematic elimination. (So, isolating x_1 in row 1, and x_2 in row 2).

\[3x_1+6x_2 = -3\] \[5x_1+7x_2=10\]

Answer 1

Now heres my question. In all the examples in class, the coefficients were always multiples and thus, easy to eliminate by multiplying one row times a constant and adding to the other. In this case, I cant multiply 7 by anything simple to get 6 obviously, so my question is: Can I multiply row 1 by 7 to get 42x_2 and row 2 by 6 and eliminate that way? I just want to be sure that operation is legal.

Answer 2

Since you have subscripts on "x". Does that mean you're using gauss-elimination?

Answer 3

looks like it

Answer 4

I haven't heard it called that. This is for linear algebra, and could also be done with augmented matrices. Ive just never done it before and dont want to start doing things Im not allowed to heh.

Answer 5

it is good u are think of how to do it rather than relying on your calculator

Answer 6

well, i'd first start by dividing row 1 by 3 to set it to as a standard matrix with 1 coefficiient on a11

Answer 7

1. Then multiply R1 by 5
2. R2-R1
3. divide R2 by -3
4. 2(R2)
5. R1-R2

solved.

Answer 8

cool thanks! This is new to me, I appreciate the help.