Apattern is made by toothpick squares. select the series that represents the number of toothpicks added to a picture to get the next picture to the right. pretend the first picture has no toothpicks.
4 + 12 + 24 + 40 + ; rule is an = 2(n2 + n)
1 + 2 + 3 + 4 + ; rule is an = n
1 + 4 + 9 + 16 + ; rule is an = n2
4 + 8 + 12 + 16 + ; rule is an = 4n

the first one has one square the next one has 4 the next one has 9 and the last one has 16

Each person in an it department of 25 people works on at least one of 3 major projects: system security, program implementation, platform development. 10 people work on system security, 13 work on program implementation, and 12 work on platform development. 4 people work on system security and platform development, 5 people work on program implementation and platform development, and 2 people work on all three projects. how many people work on system security and program implementation?