algebra system of equations
posted by luckybee on .
solve
X^2 + Y^2 =70
Y= 2X + 5

since y = 2x+5,
x^2+y^2 = 70
x^2+(2x+5)^2 = 70
x^2 + 4x^2+20x+25 = 70
5x^2 + 20x + 25 = 70
x^2 + 4x + 5 = 14
x^2 + 4x  9 = 0
x = (4±√52)/2 = 2±√13
y = 1±2√13