let's call the solutions x₁ = (5 - 2√7)/3 and x₂ = (5 + 2√7)/3
then the equation is (x-x₁)(x-x₂) = 0
if you fill that in you get a lot of numbers which you can recognize as ax²+bx+c=0.
step-by-step explanation:
you can see that a=1 (there is just an x²)
b = (-5 -2√7 + 2√7 - 5)/3 = -10/3
c = -2√7)/3 ) * (-5+2√7)/3) = -1/3
so your answer is 3x^2 – 10x – 1 = 0