
Quadratic formula is

'a' is the coefficient of x^2 = 4
'b' is the coefficient of x = 2
'c' is the constant = -1
Now we plug in all the values in quadratic formula



The above one is the substitution of values of a,b,c in quadratic formula.
Answer:
36 minutes
2 rounds for Priya
3 rounds for Ravish
Step-by-step explanation:
The answer is the LCM (least common multiple) of 12 and 18.
12 = 2^2 x 3
18 = 3^2 x 2
=>LCM of 12 and 18 = 2^2 x 3^2 = 4 x 9 = 36
=> After 36 minutes they meet again at the starting point
=> At that time, Priya has completed: 36/18 = 2 rounds
=> At that time, Ravish has completed: 36/12 = 3 rounds