the distance from the origin is 5, so
sqrt(x²+y²)=5
x²+y²=25
substitue y=x²
y+y²=25
y²+y-25=0
solve using calculator or the formula
to get
y =( -1+sqrt(1+4*25))/2
or y = (-1-sqrt(1+4*25))/2
the second solution is rejected because a square cannot be negative
the value of x is the positive or negative (sqrt... or -sqrt...) or y