Question

a) {x-y=4 {2x-y=9
b) {3x-5y=17 {5x-7y=31
c) {x+3y=8 {2x-5y=5

Answer 1

a)
{x-y=4 *(-1)
{2x-y=9
:
{-x+y= -4
{2x-y=9
------------(+)
x=5


2x-y=9
2*(5)-y=9
10-y=9
-y=9-10
y= -9+10
y= 1


s ( 5 , 1 )



b)
{3x-5y=17
{5x-7y=31
:
:
{3x=17+5y
{5x-7y=31
:
:
{x=17/3+5/3y
{5x-7y=31
:
:
5 (17/3 + 5/3y ) -7y=31
y=2


x= 17/3 + 5/3 *2
x=9


s ( 9 , 2 )


c)
{x+3y=8
{2x-5y=5
:
:
{x=8-3y
{2x-5y=5
:
:
2 (8-3y)-5y=5
y=1


x=8-3*1
x=5


s ( 5 ; 1 )