-5y^2 + 2y + 2 = 0
y = -2 ± ✓4 - 4*-5*2. /. -10
y = -2 ± ✓44. / -10
y = -1 ± ✓11. / -5
(-1+✓11)/-5. and (-1-✓11)/-5
Answer: There would be 12,000 bacteria 8 hours after the initial infection.
Step-by-step explanation: You start with 25 cells and if they divide every 15 minutes, 25 multiplied by 15 gets you 375 cells every quarter of an hour. Then if you multiply that by the 32 quarter hours, you get 12,000 cells. To check that you can also multiply 25 by 15, still 375, then 375 by 4 for each quarter of the hour, then that gets you 1,500 cells every hour. If you multiply that by 8 for the 8 hours they have time to divide, you still get 12,000 cells.
I hope this helps!
I think the answer is 12.9
Answer is option 4. working out attached
hope it helps :)