What are the x-coordinates of the solutions to this system of equations?

x2 + y2 = 16
y = x + 4

A.) -4 and 0

B.)4 and 0

C.) -2 and -3

D.) 2 and -3

Question

What are the x-coordinates of the solutions to this system of equations?

x2 + y2 = 16
y = x + 4

A.) -4 and 0

B.)4 and 0

C.) -2 and -3

D.) 2 and -3

anonymous · Answer

@wio

myininaya · Answer

Did you try replacing y in the first equation with x+4?

anonymous · Answer

Im not sure if I did it correctly but I got B @myininaya

myininaya · Answer

If you think it is B, you can check it by pluging your answer into the equations given.
If both equations are satisfied then you did good.

myininaya · Answer

Well first you would need to find y though for both x's

myininaya · Answer

You can use that bottom equation. 
It is the most easiest.

anonymous · Answer

You don't need to actually solve the equation.  In this question you can just substitute in the answers for $x$ and see which answer is consistent.

myininaya · Answer

So you have x=4 or x=0
If x=4, then y=4+4=8  (Plug in (4,8))
If x=0, then y=0+4=4  (Plug in (0,4))

anonymous · Answer

I re-did it and got A as my answer

myininaya · Answer

Cool stuff.
That answer is actually correct.

anonymous · Answer

thank you guys @myininaya @wio !