The initial equation is:

Let's transform it for x:

... distract 5:

... divide both sides by 5:
Answer:
y=-x^2 is just y=x^2 reflected over the x-axis. In other words, the parabola is upside-down.
Step-by-step explanation:
We can subsitute since
23x+4=y and
4-2x=y
therefor
23x+4=y=4-2x
so
23x+4=4-2x
minus 4 on both sides
23x=-2x
add 2x to both sides
25x=0
divide both sides by... uh oh
I guess x=0
sub
4-2(0)=y
4-0=y
4=y
the solution is (0,4)