Question

-x-3y=14 x=4y solve using substitution

Answer 1

Solve both equations for one variable.  Since the second equation is already solved for $x$, we'll solve the other one for $x$.

$x=-14-3y$ and $x=4y$ are our two equations.  

Now we can assume that if $x = -14-3y$ and $x=4y$, we can assume that $-14-3y = 4y$.  If we solve for $y$, we get that $y=-2$.  Plug in $y=-2$ into either one of the equations, I'll use $x=4y$.  $x=4(-2)$ so [/tex]x=-8[/tex].  Know we know what $x$ and $y$ are, so we can put it in an orderned pair:  (-8,-2)

Answer 2

Using
 f1(x)= -x=3t =14

with f2(x) as x=4y

f1(f2)= -x-3y=14
F1(4y)= -(4y)-3y=14
           = -4y-3y=14
           = - 7y=14
           = y= -2

Using the value of y, solve fo rx by entering the value in the original form of f1 or f2

-x-3y=14
-x-3(-2)=14
-x+6=14
x=-8

OR
x=4y
  =4(-2)
  = -8

Thus the solution is (x,y) = (-8,-2)