78 ≡ 1 (mod 7)
78 ≡ 0 (mod 7)
8980576÷195
lim f(x)
x->2
f(x)= $x^{2}$ -1
solve 78 is congruent to 0 (mod 7)
6786318
6786317
15x^2-347.88x+20063.4=0
6786316
solve 78 is congruent to ? (mod 7)