SOLUTION: Please help me solve {{{ 3x-2y=7 }}} using Cramer's rule. {{{ 5x+7y=4 }}} What I have tried is. Dx=|7 -2| Dy= |3 -7|

Algebra ->  Matrices-and-determiminant -> SOLUTION: Please help me solve {{{ 3x-2y=7 }}} using Cramer's rule. {{{ 5x+7y=4 }}} What I have tried is. Dx=|7 -2| Dy= |3 -7|       Log On


   

Question 845527: Please help me solve +3x-2y=7+ using Cramer's rule.
+5x%2B7y=4+
What I have tried is.

Dx=|7 -2| Dy= |3 -7|
|4 7| = 49-(-8) |5 4| 12-(-35)
________ -------- = 57/31 _________= -------- = 47/31
|3 -2| 21-(10) |3 -7| 21-(-10)
|5 7| |4 7|

The answers I get wont work when I try and plug them in. Is there a step I am missing?
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi,

%28matrix%282%2C2%2Ca%5B1%5D%2Cb%5B1%5D%2Ca%5B2%5D%2Cb%5B2%5D%29%29= a%5B1%5Db%5B2%5D-a%5B2%5Db%5B1%5D

Yes D = 31 = 21+10

D%5Bx%5D+=+7%2A7+%2B+8+=+57          x = 57/31

D%5By%5D+=+3%2A4+-5%2A7+=+-23        y = -23/31

CHECKING our answer***

 3x-2y= 7

3%2857%2F31%29+-+2%28-23%2F31%29+=+171%2F31+%2B+46%2F31+=+217%2F31+=+7 

Wish You the Best in your Studies.