there are 2
if we use determinant
in form ax²+bx+c=0
b²-4ac is the determinant
if the determinant is:
1. greater than 0, it has 2 real roots
2. equal to 0, it has 1 real root
3. less than 0, it has 0 reall roots
given
x²-18=0
1x²+0x-18=0
b²-4ac=
0²-4(1)(-18)=
0+72
72>0
2 real roots
A is answer
alternatley, you could solve
x²-18=0
x²=18
sqrt both side, rmember positive and negative roots
x=+/-√18
x=+/-3√2
x=3√2 and -3√2
2 real roots
