How to determine how many times a function will cross the x axis?

What is the smallest integer n such that n\sqrt{2} is greater than 20

1. there are 25 students who started computer programming in elementary school and 25 students who started computer programming in middle school. the first group had a mean final project grade of 95% and the second group had a mean final project grade of 92%. the line plot shows the differences after 10 rerandomizations. determine whether the difference in the means of the two groups is significant based on the line plot. explain your answer.

Solve the system of equations. y= 2x y= x^2 - 15