What are the solutions to the system of equations?

Question

What are the solutions to the system of equations?

x^2+y^2=5

y=2x

 

im so confused

Answer 1

take the expression for y in the second equation and substitute it into the first equation; you will have a quadratic equation in x.  solve it and then from that x value (or two values), find the y by using y = 2x.

Answer 2

Substitute the second equation into the first and get

 

x^2 + (2x)^2  = 5  or 5x^2  =5  nd x^2  =1 and x =  +1 or -1  Substituting for x in the second equation

Then y  =2  and y  =  -2

 

So the solutions are (1,2)  and (-1,-2)