Solve x2≡2(mod7)x^2 \equiv 2 \pmod 7x2≡2(mod7).
x≡3,4(mod7)x \equiv 3, 4 \pmod 7x≡3,4(mod7)
x≡2,5(mod7)x \equiv 2, 5 \pmod 7x≡2,5(mod7)
x≡1,6(mod7)x \equiv 1, 6 \pmod 7x≡1,6(mod7)
No solution