## m23chris 3 years ago solve using row reduction: 4x+9y=1 3x+7y=1

1. .Sam.

row reduction=elimination?

2. m23chris

im not exactly sure what you mean

3. m23chris

im trying to find x and y

4. .Sam.
5. shivam_bhalla

@.Sam. ,you are right

6. .Sam.

First make x the same 4x+9y=1 times 3 3x+7y=1 times 4 ------------------------------------- 12x+27y=3 12x+28y=4 ======== -y=-1 y=1 4x+9y=1 4x+9(1)=1 4x+9=1 Solve for x

7. m23chris

x=1 y=-1?

8. jim_thompson5910

well row reduction deals with matrices and elimination deals with systems of equations, so they're slightly different, but they get you the same answer.

9. m23chris

i need to solve it using the matrix

10. shivam_bhalla

see here @m23chris : http://www.math.hmc.edu/calculus/tutorials/linearsystems/

11. m23chris

we never really did it like this its hard to understand

12. jim_thompson5910

4x+9y=1 3x+7y=1 4 9 1 3 7 1 1 9/4 1/4 (1/4)*R1 3 7 1 1 9/4 1/4 0 1/4 1/4 R2 - 3*R1 ---> R2 1 9/4 1/4 0 1 1 4*R2 1 0 -2 R1 - (9/4)*R2 ---> R1 0 1 1 So the solutions are x = -2 and y = 1

13. m23chris

so youre dividing by 4 in the first row

14. jim_thompson5910

yes in the third step

15. m23chris

ok i get it now but i have 2 more questions involving 3 rows using the matrix can you help me?

16. jim_thompson5910

sure, just make a new question and let me know about it

17. m23chris

ok