Question 329127
I'll do one to show you how and you can finish the next 2.
1.{{{x^2 + y^2 = 25}}}
2.{{{y = 2x}}} 
Substitute eq. 2 into eq. 1,
{{{x^2+(2x)^2=25}}}
{{{x^2+4x^2=25}}}
{{{5x^2=25}}}
{{{x^2=5}}}
{{{x=0 +- sqrt(5)}}}
For each x, find the corresponding y.
{{{x=sqrt(5)}}},{{{y=2x=2sqrt(5)}}}
{{{x=-sqrt(5)}}},{{{y=2x=-2sqrt(5)}}}
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({{{sqrt(5)}}},{{{2sqrt(5)}}}) and ({{{-sqrt(5)}}},{{{-2sqrt(5)}}})
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{{{drawing(300,300,-6,6,-6,6,circle(sqrt(5),2sqrt(5),0.3),circle(-sqrt(5),-2sqrt(5),0.3),grid(1),graph(300,300,-6,6,-6,6,sqrt(25-x^2),2x),graph(300,300,-6,6,-6,6,-sqrt(25-x^2)))}}}