How can x^2-2x+4 be set up as a system of equations

We have two equations and two unknowns/variables

 

y = 2x + 4

y =  x + 2

 

We can solve by substitution or by elimination.

 

Let's try substitution.

 

Since both equations are set equal to y, set the two equations equal to one another and solve for x.

 

x + 2 = 2x + 4

Use algebra to solve

x = -2

 

Now use this value of x in one of the original equations to solve for y.

 

y = x + 2

y = -2 + 2

y = 0

 

So the solution is (-2,0).