Search 75,650 tutors
FIND TUTORS
Ask a question
0 0

okay so using the process of substitution,solve -3x+y=5 and x+2y=0, I know it seems simple, but every time i go to check my answer it comes up wrong,

Tutors, please sign in to answer this question.

2 Answers

-3x + y = 5
x + 2y = 0  => x = -2y
substitue in first equation
 
-3(-2y) + y = 5
 
6y + y = 5
 
y = 5/7
 
substitute
 
-3x + 5/7 = 5
 
-3x = 5 - 5/7
 
-3x = 30/7
 
x = -30/21 = -10/7
 
check
 
substitute values in 1st equation
 
-3(-10/7) + 5/7 = 5
 
30/7 + 5/7 = 5
 
35/7 =5 correct
 
substitue in 2nd equation
 
-10/7 + 2(5/7) = 0
 
-10/7 + 10/7 = 0 correct
 
 
Hi Jason;
FIRST EQUATION...-3x+y=5
SECOND EQUATION...x+2y=0
Let's take the second equation and isolate x...
x=-2y
FIRST EQUATION...
-3x+y=5
[-3(-2y)]+y=5
6y+y=5
7y=5
y=5/7
FIRST EQUATION...
-3x+y=5
-3x+(5/7)=5
Let's eliminate annoying fractions and multiply both sides by 7...
7[-3x+(5/7)]=5(7)
-21x+5=35
-21x=30
x=30/-21=-10/7
SECOND EQUATION, to verify results of first equation...
x+2y=0
(-10/7)+[(2)(5/7)]=0
(-10/7)+(10/7)=0
0=0